Because Microsoft syncs these notes to the cloud, the safest way to "find" them is via your Microsoft Account. Your notes are actually stored inside your Outlook.com account. Log into Outlook.com on any browser and look for the "Sticky Notes" icon in the left-hand menu.
Microsoft has changed the file format and storage location for Sticky Notes several times. Most modern versions (Windows 10 version 1607 and later, and all of Windows 11) use a database rather than a simple text file. How to Recover Deleted Sticky Notes on Windows where are sticky notes saved