POSSIBLE EMERGENCY!?

Hey, im freaking out! I just had Wyatt up at the park and he ate a piece of firework. It's probably a 6 inch long string with an approx. 2x2 little tarp square ( no explosive piece) i called the emergency vet and they said they have no way to tell what will happen and i should bring him in (80 to bring him, the rest is extra) He is acting fine...he's actually looking for food as we speak. Any suggestions what i should do?? I don't want to take him to this vet that i cant afford right now if i dont have to...