Kayla, I am sorry for you to have experienced this. RPD will not be taking this theft seriously as there is no money or publicity involved in trying to recover it. I am sorry, but that is reality. Unless the bike involved with some major crime, the odds of recovering it are nill.
I would share a few ideas though.
First, most of us have cellphones with cameras on them, so take a picture of the person you are interacting with. A face (along with the phone number and other info) will make the cops job easier, and there is a chance that a cop might recognize the thief.
Second, you can do a Bing search on the phone number, there are sites (pay) that you can use to check out someone. During a search, there are some sites that (if reported) will pop up. (Although this is usually for phone scammers.)
Third, if you are interested,
www.phonedetective.com is a reliable site for a search with a phone number. A report will cost $14.95 for a single search, but be advised that a burner cell might draw a blank. It might be worth the effort, and if you choose to and if successful, you can contact RPD and amend the report. (If it makes the RPD's job a little easier, they might do something.)
Fourth, I implore you to not try to take revenge on the person, he isn't worth the trouble. Leave his cellphone number alone. As fun as it might seem, do not post it to a gay dating site (CL or BP) to have people blow the phone up and making him possibly disconnecting it. Don't try to find the person yourself, again you might get into trouble, legal or health wise.
Finally, for future reference, a motorized vehicle that you want to sell, should only have a little bit of gas in it, so if someone wants to take off, they won't get far.
I know this won't count for much, but I hope that you are able to recover the bike.