It will only shows if your shop has the item at a low enough price for it to be in the results in the first place (prices of 0 do not count). There was a bug where that wasn't working correctly before, but it was fixed before you posted this. If you're seeing this happen where your shop has the item priced at a lower price than the highest showing on the shop search, it definitely needs to be looked at, though!
I'll look in to the possibility of showing your shops with no/higher prices, but I don't think it's very likely to happen, sorry.
that could definitely be the case. hmm i'll see if i can figure out something for that (like make the random ordering prioritize your own shops more?? it probably still wouldn't be foolproof though..). right now it orders all of the shops that have the item for the same price totally randomly (for fairness). hmmmm