Started a new top bar hive this spring and it was going well until early June. Between early June and yesterday something happened. Checked on them and the comb was full of wax moths. I'm not really sure what happened. There weren't even any bees left in the hive. I wouldn't have waited that long between visits but I had a new relationship that took all my time. Unfortunately the relationship was with a cardiologist, but thanks to modern surgical technology I'm feeling much better again.
Sorry you lost your bees,,,,, glad you are better. The humor "relationship" is a good one.
Blessings
They probably swarmed and ended up queenless.
They also could have absconded. That is happening more and more now. I had it happen to a healthy, strong observation hive.
Jim
You've called this a 'top bar' failure - but just in case this should influence a forum reader's decision to adopt this style of beekeeping - this unfortunate loss has nothing to do with top bars as such. It could have happened within any style of hive, and it could well have been the same outcome whether you had inspected them regularly or not.
Bad luck - hope it doesn't put you off trying again.
LJ