weapon swap bug? weapon disappeared

I'm not quite sure what happened but yesterday my weapon disappeared when I was trying to replace my weapon (with mouse) from slot 1 to slot 2 and clicked weapon swap button at the same time. Then I closed inventory and tried to attack and I noticed I don't have weapon so it automatically swapped back to slot 1. Then I opened inventory and second slot was empty indeed. I did everything very fast, almost at the same time but I was doing it before without issues.

Did anyone experience something similar?

PS: Not sure if this matters but at the same time 2 ppl were spamming abilities like crazy at my hideout.

So weapons from one of the slots are missing? It should not of been possible to drop them in hideout, as you get the warning message. You had the second set equipped at the time and had not moved it out for crafting or some other reason?