The loanable funds argument is not correct. If someone wants to bury their money that doesn't shrink the supply of capital in the economy or has any effect in the market for loanable funds, it just makes the rest of the money worth more.

The opposite of someone burying their money (or staking it) is for someone to come out with new money out of nowhere (for example, money that was previously buried, or money just printed). These actions cannot generate wealth just like burying money can't destroy wealth.