Federal agencies would not use a city police department to store evidence.
Destruction of evidence would not result in the pending dismissal of charges as was shown. There would still be digital photographs, witness testimony, and other items not destroyed.
That ten hour-time limit was a piece of overly-dramatic license. As the local police, alone, would have been able to legitimately hold Alan Van Scyop for a maximum of 72 hours (three days) before having to either formally charge him or let him go.