Just out of curiosity, was Swappa any help? I buy stuff off there occasionally and it would be good to know if they are helpful, or useless if a transaction goes bad.
Swappa will help where they can, but really the website serves as the middle-man...and really just that. You don't get the added protection of ebay, but you also typically pay less in fees.
That being said, paypal provides a pretty robust protection, and you should be fairly safe if you take precautions. If the phone is worth over 250, then make sure you get a signature confirmation...that is required by paypal.
But keep this in mind, if you are the seller, the buyer is ALWAYS right. Paypal is quicker to side with the buyer than the seller. That is why you take before pictures, and you get signature confirmation. That way, if they buyer tries to pull something, you have proof. Worse comes to worse, they ship it back and you refund them.
Really the same can be said for ebay, though I believe there may be some other protections in place. Honestly, I have been using swappa lately and enjoy it. Just got to be smart enough to be careful.