If you persisted the buyback screen beyond someone exiting the shop to open their inventory normally then it would be pretty reasonable to say. As it stands you can accidentally exit the shop briefly and the entire buyback history has vanished. It doesn't even wait for you to run a mission. That functionality without the tolerance of 'oh shit I think I sold the wrong thing' ends up being a false sense of security that handles obvious mechanical input errors rather than autopilot errors one tends to recognize shortly after the fact.

Apart from that I've never had issues with priority assignments.

I suggest you post a reply here directed at @Marcopolocs in regard to the question if they can restore a lost item
I know they can use your character to do things with your account but I'm not sure they'd do this. It would take a lot of time on their end to deal with these requests I would suppose. But it'd never hurt to ask.

There was an issue with war zone missions in the past not granting the glory rewards it showed at the end mission screen.

I suggest you take screenshots of your glory count before a priority assignment, of the rewards it shows you upon mission completion and your glory count after the mission as proof of how the rewards behave for priority assignments.

Then make a separate post with that as title and post the screenshots in there.

It depends on their current backlog but I'm sure when they have the time they'll pick that up.

But no worries, on later levels you can easily get 70+ glory per mission.

Even +100 if you use the right tarot cards.

This is only valid before you close the trader screen. If you exit the buy/sell screen, it is lost forever.

You can buy back what you sold by selecting the trader section of the screen and moving through the tabs. You'll notice the tabs where your sold items are listed have a little arrow next to their icon.

Sry for your loss.

To be honest, for new players this loss can be very annoying but if you use the tarot for increased chance to receive shards you'll get it back over time. The amount of sockets you have on an item increase the sell prices, not sure if socketed shards or codes do. To get enough credits to level up shards, sell your intels. They are worth 200k a piece.