You may be currently prohibited from possessing a firearm or ammunition under federal law, 18 USC section 922, because of the felony...

Call the clerk of court and see if they have a copy available.

You might consider visiting with a local criminal defense lawyer to see whether your state has a speedy indictment rule.

Yes, an officer can run your registration through dispatch at any time and for any reason. No reasonable and articulable suspicion needed.

The felony conviction may prohibit you from possessing a firearm or ammunition under federal law, 18 USC section 922.

You cannot possess a frearm or ammunition while under indictment for a felony under federal law.

Yes, the investigation could lead to other charges.

You might file an application for the return of seized property.

It's likely that you and your vehicle were not listed on the search warrant because the feds could not have anticipated you appearing at the time...

You will likely have additional time to prepare for sentencing at a later date. There could be a presentence investigation ordered by the court. ...