Etsy has now made it possible to search treasuries. This is something I wished for when I first started on Etsy and couldn't figure out why they didn't already do it. The main way to find out if someone included one of your items in a treasury was to use an outside site like Craftopolis that use Google Analytics information to show what treasuries you may be included in. It worked decently enough, but depended on somebody clicking on your item in that treasury at least once in order for it to show up. Newbies on Etsy don't know that right away and don't automatically click on each item in their treasury when they create it. Searching the Treasury now works like the other searches. You can search for a term like beaded or cowboy, but I believe this part depends on what tags the treasuries' curators included. The best part is that you can search for your shop. If you just enter the name of your shop in the search box while in the Treasury, you will get all of your treasuries you have created plus any that have items from your shop. Putting curator: yourshopname in the search box will give you all the treasuries you have created. Putting shop: yourshopname in the search box will show you just the treasuries which include an item from your shop. Of course you will want to replace yourshopname with the name of your Etsy shop. I found my items in two other treasuries this way. Since my items hadn't been clicked on in those treasuries, they didn't show up on Craftopolis.
If you like to support the Treasury concept, you will want to know the term "C&C" or "C/C." People often promote the treasuries they have made by putting links in forum posts or sharing them with their Etsy team. Others will help out by visiting the treasury and C&C or click and comment. Etsy has some magical formula for determining the "hotness" level of each treasury, with the hottest ones at the top. The number of clicks on items and comments left in the treasury are assumed to be part of the hotness formula, so clicking and commenting helps boost the popularity of the treasury. The hotter it is, the closer it is to the top of the front page, making it more likely to be seen by others. There is a time factor involved as well, so hotness fades over time. Why do people care about these treasuries? Well, they are a lot of fun to put together. I made a super challenging one once with items that had arrows and I lined them all up to lead you around the page. It was super cool, but very difficult to manage once some of the items sold. The other reason is that Etsy chooses treasuries to be featured on the front page (FP).