Earlier quoted context omitted.
I don't think there would be inflation. Inflation begins (IMHO) when there's a lot of money in circulation: too much cash chasing too few resources, bidding up prices. In a bank run, people are taking home bills because they want them to be "safe" in case the bank goes under (never mind FDIC, which most people probably do not understand). Money sitting under the proverbial or literal mattress is not in circulation, a…
It wouldn’t immediately cause inflation, but eventually they would start spending that money under their mattress, causing the amount of money in circulation to increase.
the thing that changes if the money is under mattresses is that the banks stop having money to lend and invest. I don't know if that creates inflation or not?