Kendra Little shows how to search the plan cache and query store for a particular query:
If I’m looking in SQL Server’s Execution Plan Cache, I like to use the sys.dm_exec_text_query_plan dynamic management view. This stores those XML query plans as text.
I learned about using this DMV from Grant Fritchey in his post, “Querying the Plan Cache, Simplified.” Grant points out that while doing wildcard searches in the text version of a query plan isn’t fast, querying it as XML is often even slower.
This is definitely worth a read.