afaik melonotan isnt a controlled substance but is sold as a research chemical.
9 out of 10 employers that drugs test employees will only test for controlled drugs (cocaine, mdma etc). Prescription and research chemicals arnt normally tested for, similarly with steroids.

But check before you start using if its an issue. Muscletalk may be your best bet as there is likely to be a fair few police posters and others who know the score on this