Let's not forget that the robbers may not, and most likely did not, have the luxury of time to bury or hide the loot if there were a posse hot on their trail.
The smart ones would already have a stashing spot set up. Dig a hole deep enough to hold the goodies, throw it in, and then roll a preset rock on top, or drop a bush into the hole, and presto, instant concealment. Some of these gangs were chased for a week before being caught up with. In order to keep well ahead of the posse, these guys had to get rid the excess weight and travel light and fast. There were others who were caught within a few hours, and the recovery was zero. How many times have we read "none of the gold was recovered".
Give some thought to the dollar amounts of gold often claimed to have been stolen from stage coaches, trains and banks. At the time gold was $20.00 an ounce, so, $20,000.00 in gold is 1000 ozs. 1000 ozs divided by 16 ozs. to the pound = 62.5 lbs. Not terribly heavy.
$100,000.00 divided by $20.00 = 5000 ozs. divided by 16= 312.50 lbs. That's a lot of weight for 3-4 guys to be hauling. If there was any chance of escape, it, the excess weight, would have to be gotten rid of quickly.
Hope this gives you something to think about.