e-mail gets marked as replied but no reply was sent

this just happens from time to time. Most my replies are delivered and saved in my sent folder. But sometimes like this morning I reply and send. Original e-mail gets marked as replied, there is information that I replied today at 7:48 but the reply is not in sent folder and can’t be found anywhere. Recipients received my reply. Also no temporary copy is saved in trash. It had no attachment and it’s not stuck in outbox. Conversations are switched off. I didn’t find answer in existing forums here.
edit: I edited 17 mins after posting