Extraction of spilled methylamine from mud
The wording of the question (and confirmed in a comment) suggest a major problem with the scene in question. If mixing dirt with methylamine made mud, then it was either some solution of dissolved methylamine, or liquid methylamine, but not a solid methylamine salt like methylamine hydrochloride. The first scenario wouldn't make sense for the synthesis of methamphetamine, and the second case is the real problem: methylamine boils at -6oC.  

Assuming they had a solution containing methylamine that had become contaminated with dirt, the recovery would actually be pretty easy. Because methylamine has such a low boiling point, simply basifying the solution during distillation would readily separate the methylamine from anything else that could be present in the contamination.