Getting error "Time-out occurred while waiting for buffer latch type 2 for page (1:3564879), database ID 7." But a database with Id 7 DOES NOT exist
run dbcc checkdb


CHECKDB creates a database snapshot behind the scenes. This is your DBID 7.

As for the timeout, perhaps KB919155 Error message when you run the DBCC CHECKDB statement on a database that contains one or more very large tables in SQL Server: "Timeout occurred while waiting for latch". "This behavior is by design.". Is page 3564879 an IAM chain page?