I have started funding my alchemy addiction by stealing from shops and pick pocketing from NPCs. I am wondering if they ever get any contents back after I have stolen from them.
Yes, some places do restock. I can't say which types of places do, but as i'm playing a thief class, I have cleaned out several places, and occasionally when I go back (for whatever reason) the NPC's nostalgia for the lost items seems to have caused them to get new ones. The best part is, I took the good stuff, so that means instead of only finding buckets and brooms lying around, I can pick up another Grand Soul Gem.
A good example of this, is the temple of Dibella in Markarth. When I got sent there on the "hangover" quest, I cleaned it out. When I went back to hand in the quest, all the items I had stolen were back, and I was able to clean them out all over again.
I don't know if they all restock. But there are many shops that definitely do restock.
The potions, general goods, and smithing shops in Whiterun restock fairly quickly. I run through them all (especially the alchemy one) every once in a while for some easy gold and materials. I've stolen from the potions store 15+ times now, so that one definitely restocks.
I'm not sure how often they restock, but it's definitely not as long as a month. Maybe a week or so.
Contrary to the post above, I don't believe it interacts at all with the inventory of goods that are being sold by the shopkeeper. It's never had any effect on the items available to sell or her available gold. And her gold is replenished much more often than the items I stole are.
While others have stated that shops do restock after the items have been stolen, I feel I should point out a faster way to level alchemy - buy the ingredients. Buy the ingredients, make the most expensive potions, sell the potions, save the game, kill the shopkeeper, load the save, buy the ingredients, make the most expensive potions, and on and on and on.