Understand your ethics, well said.
'Apparently according to the companies policy etc.' - so you don't have a copy of it? Generally bar work is relatively easy to come by.
I cannot think of any reason why this company should need to spend this amount of time investigating a case. IMHO, many of the large leisure/retail companies have really strong central management at HQ with policies up the ying-yang and then pathetic premises managers because the pay is relatively poor and the hours are unsocial. Unless the HR linkage between HQ to its local units is strong, it's very easy for a local manager to do what he/she pleases for long periods of time if, say, the person doesn't like an employee.
If this does appear to be the situation, I'd just get another temp job anyway.