second mortgage

When a senior lien forecloses, a junior lien is wiped out.

So if the first mortgage holder forecloses, the second mortgage trust deed goes away. If the second forecloses, you'll still owe the first.

Oftentimes, if a senior lien forecloses, the junior lien holder will send a representative to the auction to defend its interests by making sure the property goes for enough to pay the junior lien as well. Or they buy it themselves with the idea of reselling. Costs money, yes. But better than losing their whole investment.