I needed to recover an old version of an SSIS package that I knew was good.  The copies in BIDS was questionable.  

Find your backup of MSDB (hopefully you have one!).  

Restore it to somewhere else on the server.  

DO NOT OVERLAY MSDB!!!

Name it something else such as MSDB_Restore

DO NOT OVERLAY MSDB!!!

Extract the files using bcp then import them into version control or back into MSDB.

bcp "select cast(cast(packagedata as varbinary(max)) as varchar(max)) from yourMSDBrestore.dbo.sysssispackages 

where name = 'YourPackageName'" queryout c:\tt\YourPackageName.dtsx -Slocalhost -T -c

Hope that helps.