There is no such thing as half an engine, you have major block and head issues, if you can’t hold the venue or valet service legally responsible then your best course of action is to put in a used engine, but install will also be expensive and you would want to go through seals, timing belt etc.

Formula 1 cars of the late ‘70s - early ‘80s used the newly developed (by Lotus) ground effects to enhance negative lift by using the forward motion of the car to create low pressure under the car using venturis in each side pod and sliding skirts along the sides to seal in the vacuum. They could generate more downforce than the weight of car, like 3,000 lbs or more - enough in theory to enable them to stick to an inverted road surface if transitioned using a helical ramp. Lotus with Mario Andretti started experimenting with the effect in 1976 after doing rolling road wind tunnel tests, inspired by the British WW2 plane the Mosquito that had radiators buried in the wings.

I have heard of , rare but not to be discounted when troubleshooting. If you suspect, feel the housing and the hose - the hose after the thermostat should also be hot when the engine is fully warmed up…