Be very careful, very,very careful. You are snooping around in contemplation of making an extremely serious allegation against a number of people of dishonestly appropriating property belonging to another with the intention of permanently depriving the other of it. If true, this will expose a number of people to prosecution for crime and to an action for damages. If false, it will expose you to an action for damages that will be expensive indeed, probably ruinous. Remember also that if large sums are involved legs get broken, snoopers get beaten up, sometimes die, and that revenge is often a long time in the cooking. If in the end you want to do something, you must firstly take your evidence ( hard factual evidence, not suspicion) to a solicitor and then do exactly as you are told. If true, your employer will reimburse the cost of the solicitor. If false, you will have to pay a few hundred pound, but that will be much better than what will otherwise be coming to you. If you happen to think of something better to do than what you are doing, you might be a lot better off going off and doing it.