Need some guidance - score dropped 141 pts just before underwriting.

My wife and I just put an offer in on a house yesterday & I today I received a notification that my FICO score dropped 141 points, which puts me in the mid 500’s. My Trans Union and Equifax scores did didn’t move. I reached out to my lender, but because it’s late on Saturday, I don’t expect him to get back to me. Long story short, I’m freaking out. Is there anyway to salvage this? What if we get a co-signer? Can we put more money down? Is there any hope?