I noticed this the other day while I was questing and wondered if it was just a one-off, but then I just had the same issue. Items that I have for sale in my shop (that are priced), are not always showing up in the shop search. It seems to be inconsistent and I have caught it a few times where I knew I had the item, but it was not showing up for me at the top when I did shop search.
More info: I was doing Quentin's quests today and I was asked for a . When I did the shop search, it gave me several user shops to buy from, and I went and purchased the item. Of course after I did so, I recalled that I had gotten that item while trick or treating the day beforehand. I wondered if I had already sold this item in my shop or if I still had it in there, after recalling the issue a few days ago where my shop's items were not always showing up in shop search. I did an item search and sure enough, I had it in my one shop and when I went to check, it was priced.
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I am on Windows 10 and using Chrome Version 86.0.4240.75. I did also test this on Safari on my iPhone and had the same issue.
I just tried going through some random items in my shop and doing shop search, knowing that I do have them priced and available in a shop. While most random items I tested with are showing up at the top of the shop search results, I did find a few items that did not, like- , , , ...
I just randomly picked like 30 or so items to test this with and those are a few I found. I did not go through all my shop items. This is happening when I click to do the shop search option via the quests, the item hovers, and also typing the item into the shop search.
Thanks in advance for your help!

This is not a glitch. Shop search only shows 30 results that are lowest-priced in shops, so your items won't show up if there are at least 30 other shops who have it priced lower than you.
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