Looks silly I KNOW - BUT…

       …look at it this way.  You've been for a small, make-weight/necessary shop, you are armed with two Walking sticks, you've forgotten ANY bag.
        Scene set?  I know one bag was recently Pensioned off, SO it seemed entirely reasonable to replace it (about a fortnight ago).
       With both hands full of sticks, and not having my little Rucksack I "tried it on" - it fit - problem solved.