I'd say odds are probably 50-50 whether it was movement or scent. I've had deer snort at both. IMHO, A snort is more like a deer's What the Heck, than a OMG!. They think something is wrong but are not sure. Many times the snort is to get you to move again in order to verify you're not another tree and/or to alert other deer in the area to a possible threat. Many times they combine a snort with a foot stomp standoff. If you were truly busted, the deer woulda been gone without snorting and taken the others with it. I've had deer snort at me on bow stand only to have other come in just a few minutes later. I've seen them snort at other animals like coon and turkeys and seen them snort at other deer.
As for hunting the same trail again.........why not? Deer have fairly short memories and are spooked all the time by various things. It when they constantly or regularly get spooked/bothered at the same place they tend to avoid it. I've missed/spooked bucks from a stand in the morning and then shot/saw the same buck from the same stand, later that same day. If it's a good trail and there is a good population of deer in the area, odds are, other deer besides the ones you may have spooked will be using it. Most times, when one gets busted when still hunting it's because they are moving to fast. When I spook deer while still hunting, it's a clear sign to me to slow down.