Being Searched at work without being told

I work in England ,UK. Some stock went missing at work and everyone in the warehouse had their lockers and belongings searched, we were not asked or made aware that this search was going on. Are they allowed to do that????

They can search the work premises and your desks etc. yes--not your personal items like your wallet or purse without your permission.

During this search, one of my zips on my rucksack may have been snagged, I'm not accusing them of doing it, It may have been done by me in the past but I don't know. I have sent an e-mail to head off my HR dept asking them to investigate it, they have not responded to it yet, I personally think that they know they are in the wrong here and don't want to reply to me. In my contract and it states: you will be required to agree to a personal search and/or a search of your baggage, personal items, lockers and car etc, when requested to do so by an authorised security officer/ designated manager. If you unreasonably refuse to submit a search in accordance with this rule you may be subject to disciplinary action.
Now we didn't even have a chance to refuse, not that I would've anyway as I have nothing to hide, but its the principal of the matter, we weren't asked to submit a search.
Do I have a case here, for invasion of privacy and for them breaking the rules of my contract??????