I don't have any way to tell whether this is a bug or not, as the algorithm for question blocks is not public. Your account was blocked from asking a question about 12 hours ago, but it is not currently blocked. As you say, you've asked 4 questions, with 1 deleted, but the deleted question actually does have a negative score. I don't know whether you still have access to the question as it was deleted several months ago. I can link to it if you'd like to see for yourself, but you can also confirm this by the fact you've earned the peer pressure badge. With that said, one deleted negative-scoring question is not normally enough to trigger a block so I'm fairly surprised that you were blocked here. In any case, so long as you maintain a positive record from here, you shouldn't get blocked from asking again.