Okay, so, a -lot- of things suck about the interfaces in spiral knights and many players can't figure out the auction house, don't understand why their first crafting won't work and why they can't put their vendor or AH bought item into a recipe, etc, etc. They also accidentally sell things to Basil or Kozma when they try to re-equip but still have the trade window open.
Well, when support used to undo such accidental sales that was fine, but as support is now telling people (at least one of my guildmates, anyway) that transactions cannot be reversed period, check the window next time... wtf.
First of all, why can you sell things to Basil -anyway-? Who wants to sell anything to Basil?
Well, maybe someone does, and as much as I hate the durn things, this might be an ideal time for a 'do you REALLY want to sell your bestest 5* sword to Basil for far less than it will take to recraft it?' pop-up question. Or you could just turn off selling things to Basil. I know you can, because you can buy but not sell with Brinks.
Also, everyone, doublecheck when at the terminal, there's no safety net anymore no matter what testimony people have posted in the past. This ain't the old Three Rings anymore.
People sell things to the vendor all the time. Haze bombs are generally vendored rather than put on the AH. Players who don't need Vanaduke tokens also vendor the 5 star gear from there.
In order to accidentally sell something to a vendor, it needs to be un-equipped. You then need to go into your inventory, click on the item to equip it, not notice it didn't give you an option to equip it and that it didn't light up, drag your mouse down to the confirm button and click that as well.
As much as it sucks that you accidentally sold your best 5* weapon to the vendor, it's not exactly an easy process if you're paying even the slightest amount of attention. I imagine that the reason they won't restore gear is that the data to confirm the legitimacy of the claim isn't easily accessible.