Pat,
It is very well possible that at one time, the effect you describe happened at PV 10,
I can assure you that it didn't.
however, the bunker may have been modified previous to the Walker Cup.
Modified in what way ?
Do you have any evidence that it was modified or is this just a wild guess ?
I can only speak to 1964 regarding my experience regarding the bunker.
The Walker Cup was in 1985
Not majorly, but perhaps they noticed a little bit of build up and fixed it, maybe even without documentation by the super.
Alex, have you ever been in or seen, in person, the DA bunker on # 10 ?
It's doubtful that three grains of sand in a week escaped the deep, ice cone shaped bunker.
Another theory is that PV has a steller maintenance crew,
Given the configuration of the bunker, that's a wild, wild theory, one borne more out of of wishful thinking than actual experience.
thus sand splash from greens is unlikely to remain in following days.
Are you suggesting that they vacuum their putting surfaces every night ? 
There would need to be serious neglect for there to be any negligible differences in contouring.
Top dressing is more likely to change contours as the sand is purposely left on the greens.
But we know that topdressing has a negligible effect on putting surface contours
To answer your question in a whole rather than parts, no I have not seen PV and yes, all of my proposals are educated guesses.
When you posted the topic, I saw an opportunity to respond with mere "food for thought", not questioning your knowledge of PV or my lack of.
In regards to my first theory, no I do not have evidence that any changes were made to the 10th DA, but perhaps that in itself is evidence. How can you be sure that the super
never did any work on that bunker undocumented?
Secondly, in response to your quote:
"It's doubtful that three grains of sand in a week escaped the deep, ice cone shaped bunker":
Have you answered your own question? You claim that sand rarely escapes the bunker, so that would mean sand would not build up on the green.
Thirdly, in comparison to many "lower" class courses you would expect more sand build up because:
- likely more play on course which means more shots out of a given bunker
- worse maintenance crews - PV doesn't vacuum their greens, but they certainly do not leave clumps of visible sand and/or sand footprints on green
- sand walkers - more people are likely to not remove sand from shoes before entering green, where the most sand is deposited directly outside the bunker upon first step. At PV hole 10, I presume the bunker is too steep to walk straight up the lip and out the top of the bunker.
A combination of these factors, with the addition of your probably "bunker shape theory" is the likely cause of the lack of sand buildup around the 10th at Pine Valley.
Lastly, in response to
"But we know that topdressing has a negligible effect on putting surface contours":
I highly disagree.
Improper top dressing has had noticeable affects on putting contours.
From an earlier Tom Doak post:
Do the green contours change in the process? Yes, if it's sloppily done. Plus, on hillier sites with elevated greens, there seems to be extra topdressing at the fronts of the greens which makes the approaches very steep and wrecks the ability to play low shots into the front hole locations. I saw a lot of that at Cypress Point the last time I made a tour of it.
How much can things change? Well, to me the classic example is Yeamans Hall. In the 1930's, they reduced the size of the greens to save $$ on the maintenance budget, but because the greens were common bermudagrass and quite slow, they topdressed heavily to give it some speed. By the time I first saw it, the smaller area of the new greens had been built up twelve to fourteen inches from original grade ... it was like a mushroom was growing out of the original green. There was no hint of the ridges and swales which were on Raynor's plan of the greens and which presumably had been buried underneath all the topdressing. When we rebuilt those greens, we took the sand and spread it out over the entire pad for the original greens, but we had to look back to the plans to get a sense of what sort of contours to restore.