Sanity Warp scroll
 

I scribed the level 16 enchanter spell Sanity Warp, but the scroll did not disappear. I was able to sell it afterwards, it was not a graphical bug.

I had the same thing happen, and I think it was the same spell. I thought I had accidentally bought 2 copies. Then it also happened again the other day with the level 20 spell Tashani.

had similar experiences as you two, think it was tepid deeds, one of the thicken mana
line of spells and strip enchantment i believe, definitely happened to both researched and
vendor bought spells though

Forgot to mention, I scribed Tashani and all was well. Then I zoned and the scroll appeared on my mouse cursor.

Does anything like this happen anymore?

This happens a lot with food and drink, in my experience. I'll have 5 units of rations, buy 15, and have a full stack plus a spare in my bag. The merchant only charges for the price of 15 rations.
I have not seen this on anything besides food/drink.