I hate to Disagree, but the first effective freezers were patented in the 1840s, and would not have been that uncommon at the end of the 19th century.....

Now, if our hero came back into town in 1885, settled down, had a family, and had the son grow up into a teenager before his past caught up with him, we must be looking at 1900 or so.

I'm afraid we really have to be thinking of Idaho as totally beyond civilisation, a backwater of no note and irredeemable barbarity, to account for the lack of freezers in which to bury the gold. Either that, or Gluon has made a mess of the time-space condominium again.