Maybe it's a glitch?

This has never happened to me before.

Datalost? or did u forget to take it out from the mutation machine/pet booster?

No. i checked those

Maybe u used sell all without fav-ing the pet

No, the pet was favorited and i never use sell all

Most likely data loss

Umm is it in ur hotbar?

No

Just datalost then i guess, id prolly trade for a sloth cus the datalost report on discord does nothing

The sad thing is tho, i dont really have anything to trade for it