I accidently closed and locked my case with the tremolo arm on in a rush to get somewhere. what damages/defects should I be looking for.

If it's weakened is that fixable. And how do I tell.

Duuuuude! Breaking the arm off at the screw suuu---u-----kkkks!! It's not impossible to get out but you would need the right tools or have to take it somewhere.

If it didn't snap off when you shut the case then you're probably alright. I mean think about it, you're talking about pieces of steel up against the inside of a padded case. Best case, nothing happened. Worst case, the arm snaps off. The arm bending to varying degrees sits right in the middle there. I think you'll be fine though.
MULLY

Nothing should happen other than creating a new and probably temporary impression in the padding inside the case.

If an arm snaps off merely closing the case, said arm was no good to begin with. Consider: Any tremolo arm is subjected to more force under normal use to than the case would ever impress on it.

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You dig?