I'm pretty sure there's no way to simply revert to the previous checkmark status _from_within_PT_.
Also, as you're working along as you accidentally mark things, there's no way to revert to an intermediate position between the current state and the state at the last Send/Receive (or whenever you saved in History).
However, PT's history system is extremely powerful, even more powerful that PT gives you access to. So it definitely is possible to revert to the state things were in at the last Send/Receive. In this case, that would be by setting the file "DerivedTranslationStatus.xml" back to the way it used to be. If you're interested, send me a private message and I'll outline the steps. Beforehand, though, I'll say 1) it's always a good question whether the amount of work to install the external tools to manipulate the history is worth the time, and 2) you'll lose any checking status you've added in the time since the last Send/Receive.