[Nexus 7 Q&A, Help & Troubleshooting] shonangreg:
OK. Found it, thanks, though there is no "recovery.log" file with that exact name there. Here are the three files there:

/cache/recovery/last_install

/cache/6ece895ecb23.signed-nakasi-JDQ39-from-JOP40D.6ece895e.zip
0

/cache/recovery/last_locale

en_US

/cache/recovery/last_log

Starting recovery on Tue Mar 26 13:15:10 2013
recovery filesystem table
=========================
0 /tmp ramdisk (null) (null) 0
1 /sdcard vfat /dev/block/sda1 (null) 0
2 /system ext4 /dev/block/platform/sdhci-tegra.3/by-name/APP (null) 0
3 /cache ext4 /dev/block/platform/sdhci-tegra.3/by-name/CAC (null) 0
4 /data ext4 /dev/block/platform/sdhci-tegra.3/by-name/UDA (null) -32768
5 /misc emmc /dev/block/platform/sdhci-tegra.3/by-name/MSC (null) 0
6 /boot emmc /dev/block/platform/sdhci-tegra.3/by-name/LNX (null) 0
7 /recovery emmc /dev/block/platform/sdhci-tegra.3/by-name/SOS (null) 0
8 /staging emmc /dev/block/platform/sdhci-tegra.3/by-name/USP (null) 0

I:Got arguments from /cache/recovery/command
locale is [en_US]
can't open /dev/tty0: No such file or directory
framebuffer: fd 3 (800 x 1280)
installing_text: en (324 x 38 @ 411)
erasing_text: en (109 x 38 @ 312)
no_command_text: en (172 x 38 @ 312)
error_text: en (64 x 38 @ 312)
Command: "/sbin/recovery" "--update_package=/cache/6ece895ecb23.signed-nakasi-JDQ39-from-JOP40D.6ece895e.zip" "--locale=en_US"

ro.boot.serialno=015d2578a7180806
ro.boot.bootloader=4.13
ro.serialno=015d2578a7180806
ro.bootmode=unknown
ro.baseband=unknown
ro.bootloader=4.13
ro.hardware=grouper
ro.revision=0
ro.factorytest=0
ro.secure=1
ro.allow.mock.location=0
ro.debuggable=0
persist.sys.usb.config=mtp
ro.build.id=JOP40D
ro.build.display.id=JOP40D
ro.build.version.incremental=533553
ro.build.version.sdk=17
ro.build.version.codename=REL
ro.build.version.release=4.2.1
ro.build.date=Tue Nov 20 00:55:07 UTC 2012
ro.build.date.utc=1353372907
ro.build.type=user
ro.build.user=android-build
ro.build.host=vpak21.mtv.corp.google.com
ro.build.tags=release-keys
ro.product.model=Nexus 7
ro.product.brand=google
ro.product.name=nakasi
ro.product.device=grouper
ro.product.board=grouper
ro.product.cpu.abi=armeabi-v7a
ro.product.cpu.abi2=armeabi
ro.product.manufacturer=asus
ro.product.locale.language=en
ro.product.locale.region=US
ro.wifi.channels=
ro.board.platform=tegra3
ro.build.product=grouper
ro.build.description=nakasi-user 4.2.1 JOP40D 533553 release-keys
ro.build.fingerprint=google/nakasi/grouper:4.2.1/JOP40D/533553:user/release-keys
ro.build.characteristics=tablet,nosdcard
ro.opengles.version=131072
wifi.interface=wlan0
rild.libpath=/system/lib/libril-icera.so
rild.libargs=-e wwan0
persist.tegra.nvmmlite=1
ro.audio.monitorOrientation=true
debug.nfc.fw_download=false
debug.nfc.se=false
ro.sf.lcd_density=213
ro.carrier=wifi-only
wifi.supplicant_scan_interval=15
tf.enable=y
drm.service.enabled=true
dalvik.vm.heapstartsize=8m
dalvik.vm.heapgrowthlimit=64m
dalvik.vm.heapsize=384m
dalvik.vm.heaptargetutilization=0.75
dalvik.vm.heapminfree=512k
dalvik.vm.heapmaxfree=8m
ro.config.ringtone=Girtab.ogg
ro.config.notification_sound=Tejat.ogg
ro.config.alarm_alert=Cesium.ogg
ro.com.android.dateformat=MM-dd-yyyy
ro.com.android.dataroaming=false
ro.url.legal=http://www.google.com/intl/%s/mobile/android/basic/phone-legal.html
ro.url.legal.android_privacy=http://www.google.com/intl/%s/mobile/android/basic/privacy.html
ro.com.google.clientidbase=android-google
ro.com.android.wifi-watchlist=GoogleGuest
ro.error.receiver.system.apps=com.google.android.feedback
ro.setupwizard.enterprise_mode=1
keyguard.no_require_sim=true
ro.facelock.black_timeout=1250
ro.facelock.det_timeout=1500
ro.facelock.rec_timeout=2500
ro.facelock.lively_timeout=2500
ro.facelock.est_max_time=1000
ro.facelock.use_intro_anim=true
ro.media.effect.bgdropper.adj=0.2
camera.flash_off=0
ro.setupwizard.gservices_wait=true
ro.com.widevine.cachesize=16777216
ro.setupwizard.wifi_required=true
dalvik.vm.dexopt-flags=m=y
net.bt.name=Android
net.change=net.bt.name
dalvik.vm.stack-trace-file=/data/anr/traces.txt
init.svc.ueventd=running
init.svc.recovery=running

Finding update package...
I:Update location: /cache/6ece895ecb23.signed-nakasi-JDQ39-from-JOP40D.6ece895e.zip
Opening update package...
I:read key e=3
I:read key e=3
I:2 key(s) loaded from /res/keys
Verifying update package...
I:comment is 1604 bytes; signature 1586 bytes from end
I:whole-file signature verified against key 0
I:verify_file returned 0
Installing update...
Verifying current system...
file "/system/bin/debuggerd" doesn't have any of expected sha1 sums; checking cache
failed to stat "/cache/saved.file": No such file or directory
failed to load cache file
script aborted: assert failed: apply_patch_check("/system/bin/debuggerd", "a2323a0c8e245e3879d6b8beff6b2c4802045271", "df2e705da097e4d535b4f4d98fab3bd76601e76c")
assert failed: apply_patch_check("/system/bin/debuggerd", "a2323a0c8e245e3879d6b8beff6b2c4802045271", "df2e705da097e4d535b4f4d98fab3bd76601e76c")
E:Error in /cache/6ece895ecb23.signed-nakasi-JDQ39-from-JOP40D.6ece895e.zip
(Status 7)
Installation aborted.
I:Saving locale "en_US"
I:timed out waiting for key input; rebooting.
I:Saving locale "en_US"

Is all of this because I didn't save a checksum when I rooted and flashed before?