I agree with Mr. Arbuckle. Unless you have really good, solid evidence proving that a lawyer who has appeared for a party is not really that party's lawyer, filing a motion challenging his or her authority would be shooting oneself in the foot, especially in federal court where the judges do not tolerate nonsense that needlessly consumes their time.
No, which is just as well, because only pro se and really stupid lawyers would ever try to use that rule.
This is not legal advice. You should always discuss the specifics of your issue in person with an attorney. Be aware that there are time limits on all claims that depend on the kind of claim, so do not delay in seeking an attorney.