This is a highly unusual situation so I doubt that there are specific forms available that you could follow. Since the amount involved appears to be $400.00 it doesn't seem practical to hire an attorney. I would suggest that you go to the law library to see if you can find any forms for motion for return of bail and then used that as a template to write your motion and allege the facts as they occurred. If you were represented by the public defender see if they can help you. You could check with the District Attorney's Office to see if someone there can help you. They have no interest in seeing you financially punished for a mistake mad by the justice system and certainly wouldn't oppose your motion, so they may even help you draft the motion or simply draft an unopposed order for the judge to sign.
Have you tried to go to the information counter to get a certified copy of the withdrawal and taking the copy to the basement cashier for your refund? If not, try that first before going through the trouble of filing a motion. Granted I am only in Philly on occasion, but I have not had any problem having clients get bail refunds this way. Sometimes there is a delay with processing. But that is the only problem I have had. If this suggestion works for you, follow up with a post.
There's not really going to be a form for this.
I'd ask the attorney that's helping you with the other case to help you with this. It should be pretty trivial.
Barring that, you can probably get away with a document that has all of the proper case information at the top--copy off the other paperwork you've got for the case--which explains, in clear and simple terms, what it is that you want. Put your name at the bottom, sign and date it, and give it to the Clerk of Courts.
This answer does not constitute legal advice and does not establish an attorney-client relationship.