i thought you knew that - Someone does something dumb or sneaky and when they get caug

Someone does something dumb or sneaky and when they get caught, they say this like they're being extra lazy and you're the dumb one.

'You didn't know I took your phone?' 'I thought you knew.'

'You didn't know I told everyone your crush?' 'I thought you knew.'

'You didn't know I failed your test?' 'I thought you knew.'