It’s possible that if caulk was used, it didn’t have time to dry and immediately carked it. Sticking a plastic sheet over it may have helped but then they would’ve had to come back to remove it. May have just risked it to save you the money of them returning. It was either a definite return to remove whatever was covering it, or a potential return if the fix carked it.

That’s just my two cents anyway, I’m just spitballing.