I can't understand why this Landlord is being difficult, particularly if he's already lost a month of rent.

Originally lost out when higher bidder could not come up with cash for building.

I’ve heard that vegas multifamily rents dropped in Vegas  (I Didn’t/don’t own any so I didn’t notice/care) but SFR in Vegas rents rose quickly as people who lost their homes didn’t want to move their family in to an apartment. $3,000/mo lakefront rental In MN was unaffected. 

Went through way to many trades and lost way too many months to no shows or rework.

This will create opportunity, but the last thing you want is to be mid flip with no other exits on a property that had a projected profit of $20K-$30K and it's just lost that in value.

My company lost dozens upon dozens of bookings in a matter of days, totaling untold thousands of dollars.

Keyless entry is gaining popularity - no lost keys, some even allow opening via cell phone. 

The hardest part for me is dealing with tenants who have clearly lost touch with reality and stop communicating.

That superior return will result in the investor getting their capital back and earning DOUBLE DIGIT RETURNS on their capital even if the actual results are 20% lower than projected.The above is the reason why we've delivered double digit returns to our investors and no investor has lost capital with us ever, since I started raising money from investors since 2006.

I do believe you have an obligation to replace the lost $ 10K check but there should be no risk to you in doing so.