Most (all?) items left on loungers are NOT in the valuable category, unless the book is a priceless manuscript ๐. So Regentโs liability may be minimal.
I agree OPโs letter may have been so arrogant as to be ignored. But a word while onboard, stressing satisfying the majority at the risk of offending the minority , might be more successful in dedicating a staff member to โpoliceโ the area.