Is there a way to recover your Xbox 360 gamertag without Xbox live?

Yes. You have to have a memory card or the last 360 your gamertag was on had to be an arcade version. If you have a memory card, simply go to the last xbox it was on. The look up the gamertag by going to the hard drive's memory, then gamerprofiles. There will be 2 options, delete or move. click move then move it to the MU. If you only have a hard drive you can move it the same exact way but it has to be on an xbox arcade system because these have built in memory units unlike the other 360s.