Sidorovich's "Debt"

("Interests" is also here as it's a small related task)
As you walk past the [ brick house] at Cordon, you get a weird text message from Sidorovich asking you to repay Sidorovich's debt to the stalker inside the house.
== Walkthrough ==
=== Variant 1 ===
After checking that everything seems to be in order, give 70000RU to the stalker. Travel to Sidorovich, and he will tell you it was a scam by some gang, and give you a gift to compensate for your loss.
=== Variant 2 ===
Check Sidorovich out first to verify that he really messaged you. Realize it's a scam. No money wasted, but also no gift. This variant also blocks another quest where you encounter the same scammer the second time, much later. (Vengeance)
== Notes ==
* After visiting Sidorovich's bunker, the scammer will go away, and your only option will be to talk to Sidorovich.
* Getting scammed is the only way in which you can obtain an Artefact detector in the early game. This is a rare item that you'll need for some normal and chain quests. Besides, in the follow-up quest you'll get the valuable transition that will cut your travel time substantially. (and it's required for the S.T.A.L.K.E.R. achievement)
== Bugs ==
* If you wait too long, the scammer will disappear and the task will be stuck in your PDA forever.