Who is being unreasonable here? I'll try to keep it short and neutral.
Pair of trousers left on the bedroom floor with receipts in the back pocket. Four weeks or so later, those trousers turn up cleaned on the clothes airer without the receipts. Noone knows where receipts have gone so assumed that the cleaner must have emptied the pockets and thrown them away (very unlike her, but only real explanation).
Washing is usually Partner 1's household job (as agreed between Partner 1 and Partner 2 as a trade of chores) but cleaner has started to throw in a load or two when she's here too.
Who is responsible for the missing receipts (excluding the poor cleaner!)?
Partner 2 (for leaving trousers and receipts in the floor in their own home) or Partner 1 (because laundry is Partner 1's job and therefore they are responsible when something like this happens since their delegating part of it to someone else)?
YES: Partner 1 (laundry delegator) is at fault
NO: Partner 2 (trouser leaver is at fault)