How can one distinguish an IR spectroscopy alcohol band on an organic molecule versus the alcohol bands from water in the sample?
The main working rule of a good FTIR spectrum is that everything must be bone dry! The absorbance in IR is additive just like Beer's law, i.e. your spectra is the sum of water traces in your sample as well as your suspected alcohol. There is no simple way to deconvolute it. Dry your product thoroughly in a vacuum dessicator for at least a day and re-run the IR. If your big -OH band vanishes, it means your product was not dry. If it persists, your product likely has an hydroxide group.

KBr must be oven dried well before use as well.