Hmm, no idea. It’s not something I’ve heard of before. 😅
All I can say is, the game was made from scratch in 12 days, so I’m not entirely surprised if there’s an occasional glitch.
I've investigated the issue and it looks like somehow the game thought you'd already picked up the lice.
It's on a timer, so I wonder if something interrupted it when you played it through, so that it got as far as recording the lice, but not to the point where it actually put them in your inventory.
Glad you managed to get infested though (never thought I'd have to say that... again).