Rollback transaction after recovery

Hi all,

Here is an interesting one, we have a database in Simple recovery mode on a SQL 2012 box. The log file growth was capped and got filled up by a long running transaction, throwing the database into recovery. When the database is finally recovered, DBCC OPENTRAN still shows an active transaction however the SPID no longer exists on the server. Therefore, the transaction file size remains the same.

How could possibly this open transaction be closed/rollbacked and transaction log space released?

Thanks in advance.

Nirupam