Make sure you are at the correct shelf location. For example, if you are looking for a periodical labeled QH301.S753, go to the shelves where you will find periodicals with QH300 call numbers, not QH3000 call numbers. Always ask for help at the Reference and Information Desk if you're unsure. Check the Bound Periodical Reshelving Area, located on the first level. Check the photocopiers.
Patrons sometimes leave periodicals there.
When all else fails, complete a periodicals trace form at the Periodicals Desk.