Hi @c_oreills - hard question! 
I’d definitely go with your hypothesis as well. We don’t publish a log of when accounts switch state, and if an account is protected and hasn’t given your account access, you wouldn’t see any data. This is a privacy issue, so we have no plans to change these details.
I can’t think of other circumstances that might correlate, and I’m sure it is annoying not to be able to “be sure”, but I’d imagine your guess is very likely correct in this case.