If there were no drugs present, then there were no drugs! They cannot now decide that there were drugs after all. That gets rid of the police issue.
If there were no drugs, this should not affect either your licence or your employment. If it does affect your employment, then you would obviously have a claim to bring in the employment tribunal if it affected your employment to the extent that you felt you could no longer work there (constructive dismissal) or if you were dismissed.
Can I clarify anything else for you?
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