Ants in top of flow frame

I was doing a check this morning and found the lock/unlock slot of one frame has ants nesting in it. That was confusing for a bit until I realised it didn’t have the cap on the end. I looked around and found the cap on the ground at my feet. I was fortunate to find the cap and that the mower hadn’t eaten it.

It had obviously been missing for some time as the ants were very settled. The strange thing is that I did not harvest that frame the last time I took honey from the hive. It’s frame 4 and sitting over the brood area and had an area with no honey in the middle. I have no idea how the cap fell out.

I got the battery powered leaf blower and blew into the are to clear anything loose enough to blow out. That wasn’t very successful. So I moved the frame to the end window where I can check it. When it’s fully capped I’ll harvest the honey, then swap in a new frame destined for a new hive. Then I can take the anty frame away and give it a proper cleanup - whatever that takes.