Parked car searched, found mdma, rightful owner didnt speak up.

[CdwJava]

Also, in response to cdwJava, the ranger found crystals in a baggie, but he couldn't (by the sound of his radio chatter) get a k9 unit to the area. I am under the assumption that they are MDMA crystals, based on what my friend (who owned aforementioned crystals) told me, but the ranger didnt know that at the time. The car was unlocked and parked all night, so any of my camp mates could have had access to the car.

What code sections are on the citation?

What MAY have happened is that you were cited for the marijuana, and he is going to have the crystals tested and if they come back positive he will have you charged for the felony possession.

As others have said, your friend's admission may not help you much. But, a US Attorney (or DA if charged as a state level offense) may accept that and your testimony against the other guy as part of a plea.

Consult legal counsel ASAP.