There are some warts that are just really hard to be rid of with OTC products. So even if it is a wart - your doctor can try to freeze/burn it off.
There are other types of precancerous skin spots that can be crusty and resemble a wart and they are also frozen/burnt off. So relax until you get to the derm. He/she will know which it is and since treatment is basically the same, you will be covered either way.
If treatment doesn't work and it comes back - I would suggest that you have your doctor biopsy it.