Glue

I need to know what type of glue is used to keep the side window in its track.

I used some high$$$ black window sealer;it was worthless.
Silicone is great for gaskets, and as a sealer, but its not an adhesive.
Goop held for awhile but gave loose.

The current glue is like silicone but will not let go of glass: you cant scrape it off. How can I find out what kind of glue it is ?