One way to tell if it was drumming is the spitting sound that comes before the drumming. It sounds like you are drawing air through your teeth.
It sounds like SSFFFFFTT!!!...and then the drum, VVVVVOOOOOMMMMMM. It is a very distinct sound and once you' ve heard it you won' t forget it.
It is also a very good possibility that it was a fighting purr. Either of these sounds are common in the turkey woods.
Either way you can be pretty sure you got busted.

That' s the one thing that remains pretty constant in turkey hunting.
Turkeys are the one critter I' ll chase year after year with very little success. I hunt public land and constantly get messed up by other hunters and the birds are so call shy they are almost impossible to call in, but I still have a blast messing with them.