Are you certain you didn't acquire these during the event and only just noticed them? They only dropped during the event which is long since over, but they don't have a cleanup to be removed from your inventory automatically.
Can you provide some more specific information about what you're doing and how, as well as what the end result is that you're getting? There's not much to work with here.
I'm going to need more information for this report. What platform is this issue happening on? When did this last happen? How often does it occur? With specific steps, what exactly are you doing, and what happens when you do it?
We implemented a fix a while ago to prevent failed coin challenge matches from redirecting to the Bomber Royale requeue flow, so as far as I know this issue should no longer occur.
I can't reproduce this with the reported method, if this is still happening. If you've got any more information on how to reproduce it, please update this issue.
I'm trying to understand the issue here. The quest for a bomber royale coin doesn't say that it would grant experience, so I'm not sure why you would expect it to. Is it just that this quest doesn't grant xp but counts against the 20 for the day?
Essentially a duplicate of https://trovesaurus.com/issues/view/86, we will get the mementos and trophies to all reference the correct NPC names eventually.
Do you know which enemies specifically you saw drop this? If you can name the trophies at the start of the delve that would help the most, but even just the general type of monster would help.