I was arrested and site released for 11377 poss of cont subst?

i was sitting in the used car i had just bought 3 days prior because it was going to overheat if you know anything about fords then you know not to let them overheat for cause of warped heads so the police roll up on me and ask if ive ever been arrested before. i said i had but not since 1999 when i was arrested and imprisoned for poss of controll subst but since then i had been to 3 yrs of rehab and cleaned myself up they asked if they could search the vehicle , sure no problem they found a piece of a broken pipe in one of the speaker holes it had some residue in it nothing that would be a usable amount and field tested me in which i ped all field tests given but they arrested me anyways and upon release i had to pay over 650.00 dlls in impound fees now i have a court date of april 16 did they even have cause to arrest me?