The nation’s largest hospital landlord said an unusual transaction that provided crucial financial support for one of its biggest tenants was a done deal. It wasn’t. The deal was good news for both companies, and for communities across the country concerned that their local hospitals could go broke. The landlord, Medical Properties Trust, announced the transaction in May. When it reported quarterly results on Aug. 8, it said the arrangement boosted its own revenue. But a California state regulator on July 20 ordered that the transaction between MPT and Prospect Medical Holdings be put on hold, according to the order that the regulator sent to Prospect.