I have a feeling that a senior dev left a bug on purpose to see if I would catch. Anyone else have that feeling or am I just paranoid?

after work, grab two beer and have a friendly chat with him? 🙂

I'm guessing it's more paranoia.. senior Devs make bugs too, even the odd schoolboy ones!
Depends on context too obviously, like if it's common practice to do this sort of thing, especially if you're new. But either way you'll have to flag the bug. If he did it on purpose then surely he'll congratulate you for finding it and tell you it was a test.
Or, like @heyheni says, ask him directly.

yeah the greatest improvents and ideas don't come up in meetings but with two people speaking their minds with 🍻and maybe a barbQ 🍖🥓

I've done this sometimes, specially when training people, but who knows, you probably should ask yim

Everybody is human. If he/she has or has not it doesn't matter. Work as a team and _solve_ problems that way. Don't look for issues encourage having fun resolving them. One day he/she might be the one asking you for help... you will become a senior human as well.

I know that feeling, but I have to echo the others. It's probably just a silly mistake.