Does Mrs Nick have anything to do with organising the event? If so I reckon she is running a raffle or something similar that needs a large container for the draw ~ perhapw she has responsiblity for buying flowers for a "guest of honour" and wants a bucket of water to keep them fresh in.
Didn't see the above but I was at least partially right in that she is organising. Now ~ why did she not takle the bucket with her? ~ Given that she is only too aware of your ability to "forget" her instructions.