“Yes, sir, Officer Obie, I cannot tell a lie, I put that envelope under that garbage.”
Admittedly I don't know the details of British refuse hauling, many places in the US have private haulers that are not above dumping at unlicensed dumps to save dumping charges at approved landfills.
If contracted with such a hauler you discarded mail could end up there.
And since many people do not get anything in the mail but the junk variety and at least the US mail is rather careless in the delivery of mail, your mail could end up at another address and be discarded by someone else.
If the authorities found 30 envelopes with your address on it they might have a case.