All one has to do is read the posts on ebay to know this has been a long-standing, on-going situation with MANY, MANY complaints. All new listings go through an indexing process involving more than one server. With millions of new listings, it takes a lot of time, especially considering to the complex cross-linking involved.
The indexing process also includes extra delays for certain listings, and keywords. Ebay says this is to catch fraudulent listings. Anyway the end result is sometimes a very long delay before a listing will show up in searches. When this happens, you should still see your listing on your My eBay page, or by searching by item #, which nobody is going to do of course.
Ebay themselves has recently said you should sometimes wait 12 to 24 hours, which is "normal". Some ebayers have waited days! Personally, I've had listings take 10 minutes, others take 6 hours. Grrrrr! We feel you pain.