Was the backup overwriting the older backups in the file every night or appending the backup to the file?
Restore headeronly should show you what backups are in the file.
If there's only one backup in the file, then you can only restore from that. If backups are being overwritten then the older backups are gone.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability