Suspicious mole removed came back completely normal on pathology report. Is there a chance they could have missed a melanoma?

Unlikely. In the hands of a competent pathologist the diagnosis is probably accurate. You and your dermatologist could ask for a second opinion if there is concern.
Probably not. If it was read by someone trained in melanoma pathology it would be rare. If you are concerned you can always send your pathology to a different doctor for a second opinion.
Unlikely. Many things are possible, but this would be highly unlikely (unless the wrong specimen was evaluated for you) if it was diagnosed as completely normal. Try not to worry about this possibility too much. Meanwhile, continue to check your skin for suspicious lesions and protect your skin from prolonged or intense sun exposure.
Very unlikely. If the mole was completely removed, it is extremely unlikely that melanoma was missed. If you are concerned, however, you should ask for the sample to be reevaluated.;\.