I would say assume it isn't het. If you're really wanting a guarantee het, buy from someone reputable. Unfortunately people can easily lie and get away with it when it's craigslist.
If you have pics, post them here and people can help ID if hes enchi.
If you get him be sure to do strict quarantine if you have other reptiles.
Ultimately its your choice of course, if you wanna roll the dice!
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