Instead of trigger in SQL Server loses SCOPE_IDENTITY?

Use @@identity instead of scope_identity().

While scope_identity() returns the last created id in the current scope, @@identity returns the last created id in the current session.

The scope_identity() function is normally recommended over the @@identity field, as you usually don't want triggers to interfer with the id, but in this case you do.

Since you're on SQL 2008, I would highly recommend using the OUTPUT clause instead of one of the custom identity functions. SCOPE_IDENTITY currently has some issues with parallel queries that cause me to recommend against it entirely. @@Identity does not, but it's still not as explicit, and as flexible, as OUTPUT. Plus OUTPUT handles multi-row inserts. Have a look at the BOL article which has some great examples.