You may not be hillucinating.
I thought the same thing. I got back late Tue night and Wed was day 18 for me. I worked all day to raise the humidity. I was so worried & paranoid since I had such a horrible first attempt. My BIL house, bator, & critter sat while we were out of town. So I was worried that he might not have monitared things like I would have.
Anyway, Day 19 I'd go check every once in a while and nada. Day 19 I thought I saw it move, but convienced that I was imagining things. I kept putting my ear up to the bator and would hear things, but never saw movement, so I was convienced that it was the pinging of the heating element that runs on top of my old galvanized bator. I went to run errands twice so that I wouldn't keep staring at them. I was hoping when I'd come back I'd hear or at least see some action.
Day 20 the same thing. Finally at about 11:30 pm on Fri night I thought I'd heard a peep. I had to run upstairs to get dd. She said why do you want me come down, do you think it's in your head? LOL!!!!!
I was to antsy to crochet while I waited, then I was to tired from no sleep.
Good luck and keep me posted!
Kim