Kendra Little talks about index discovery:
Whenever you set up a script to create or drop an index, you want a safety check in there. Drop the index if it exists. Create the index if it doesn’t.
Or do something else programmatically. Checking if an index exists is a pretty frequent task. But there’s no simple function to test if an index exists in SQL Server.
Good article, and in the comments, Kendra talks about the next logical step: consolidating indexes.