Mystery Oil Leak After Frontal Shunt

[Confused of Devon]

Toyota RAV 4 - 2004 2 ltr petrol.

Frontal damage after shunt with car in front, max 15 mph. Vehicle driveable. 50 miles later, major smoke from oil burning on exhaust. Oil sprayed all over engine. Oil was 1/2 way down dipstick. Car trucked to insurers repairer, who found pool of oil on engine block recess, front right hand side. They have steam cleaned the engine, test run it but cannot locate source of oil. Compression test indicates head gasket OK.
Body repairs required new front valance, air con and cooling radiators. They now propose to return the vehicle and expect me to sign it off, but if I do so and the oil leak returns I risk having to bear the cost of repairs. I do not believe this oil leak is NOT connected with the shunt. Car serviced 8 weeks ago but garage can shed no light. Any ideas as to source of mystery oil leak? This minor body repair has taken 4 weeks to date and, frankly, I have no faith in the repairers.