Another example (I am no expert) is a margin call.
If I am purchasing using $100k of margin and my collateral drops to the point that I no longer have the margin. That 100k is gone. It wasn't a real 100k in the first place, it was leveraged and backed by a volatile asset.
From a look at the M2 and M3 money supply, there never seems to have been a contraction:
https://fred.stlouisfed.org/series/M2
https://fred.stlouisfed.org/series/MABMM301USM189S
That seems to be a pretty strong argument against the money contraction theory.