Neighbors And Dog Business Don't Always Mix

Neighbors.  It's a weird relationship.  For most of us, it's just the people who live next door or across the street.  There's a usual cordiality - you know, hello and goodbye, the occasional how are you but let's face it, who's really interested?  It's a common courtesy thing.  But how about when your seemingly polite neighbors act less than polite?  Case and point.  We have a puppy.  The puppy goes outside several times a day to do her business.  Sometimes her business is well, solid business.  In most cases, like when it's not in our own yard and not down by the pond, we pick it up and dispose of it properly.  I think in the time we've had the puppy, about 5 months now, we've been remiss maybe once or twice.  My neighbor seems to disagree.
About a week ago, my neighbor stopped my daughter, presented her with some plastic bags and asked her to please pick up after our dog.  My daughter, being the polite girl that she is, apologized and assured her that indeed we do and definitely will.  I'll stop here to comment on the fact that this woman saw me that very morning and said nothing to be about the dog.  In fact, I see her almost daily, we exchange the usual pleasantries and she has never, not once, said a word about the dog or her business being in her yard.
Okay, so here's the issue.  A couple of days ago while she was mowing her yard, I noticed that she stopped, contemplated, picked something up, walked to the front of the yard (I lost sight of her here) and then came back and continued her yard work.  I thought it was odd behavior but dismissed it as just that.  Imagine my surprise when later that afternoon as I went to pick up my mail and lo and behold there was an interesting deposit so to speak right near my mailbox.  No way!  My neighbor must have come across it while mowing, picked it up and put it in my yard to make some kind of passive-aggressive point!  Eww!  First of all, how gross. Second of all, it wasn't my dog's.  Third of all, who in the world picks up poop and puts it on someone else's lawn?  Disgusting!  When I told my kids, they cracked up!  Their "solutions", I have to admit, were priceless.  My son wanted to deposit the package on her doorstep and set it on fire.  My daughter just thought it should be scooped - by a shovel or some other tool, definitely not by hand! - and flung back in her yard.  I on the other hand wanted to take my puppy over and let her leave a present in the neighbor's yard.  Needless to say, out of a sense of neighborhood harmony, I did nothing.  This time.  Next time, I hope she's got a shovel.