After the gas station holdup the 3 suspects meet along the road. The lady bandit advises the fake cop to change out of his uniform later and to get going. He had already untied his necktie, but when he reaches his car his tie has been re-knotted.
During the first robbery (at the loan company), when the loan manager follows behind the stickup man to try to obtain the license of the getaway car, he easily could have seen the fake patrol car parked outside the location. If he would have run out back at all, it would've been impossible to not have seen it as it was parked clearly out in the open.