If it's in the text of a proc / function, you can use the simple and free third-party plugin from redgate: SQL Search, there are also ways to do it with TSQL. See the answer to the question about stackexchange for searching procedures.
However, it is very likely that your proc will look for the value in a table that stores it, so it does not need to be hard-coded.
If you want to perform a simultaneous search in several columns, this link can be useful:
String search in different tables