Would the police waste their time on this?

Ok so me and my friends decided to do a little prank on a random neighbor with the old flaming poo in a bag trick but we couldnt find any dog **** so my friend used his. Hhahahaha. but anyways hes flipping out because he thinks the cops are going to sample his **** and find his DNA and hes gunna get arrested. I thought that the cops wouldnt waste their time and money on it because there wasnt anythreats involved and the beg didnt even stay on fire for more than two seconds. What do you think? will the cops test it?