.... Haven't had any problems yet but if one arises I have my permission.
It's pretty hard to argue with a "yes". And the feeling of having a printed out permission slip in your pocket is very comforting. So on the surface, your story will just serve to reinforce the notion that "see.... it was and is a good thing to ask".
And ironically, if you'd gotten a "no", you would come away with the same conclusion. It would go something like this: "See, it's a good thing I asked. Because otherwise I could have been arrested".
So whether the answer was "yes", or "no", they both equally reinforce the inherent conclusion that asking was necessary and good. Right?
But ask yourself: What other answer could they have given you ? Do you really think they'd answer like this:
"Gee that's a funny question. Why are you asking us? You don't need our permission. If there's no law forbidding, then it's not prohibited" Nope. Authority never works like that. They will bestow on you their princely "yes" or "no".
And while your particular "yes" was granted, yet I bet that someone else could go in that exact same office the next day, talk to someone else, and receive a different answer. Just based on subtle nuances of how you phrase the question. For example: Did you be sure to mention "holes" and "dig" , "take" , "remove", etc.... ?
And be aware there's been persons who, like yourself, got a "yes" , only to be accosted in the field by an angry gardener or cop. The md'r proudly whips out his "permission", only to have it promptly revoked. The busy body gets on his phone, calls down to city hall, and says ".... but he's tearing the place up!" (which isn't true, of course). And you are sent packing, and accused of getting permission under false pretenses (mincing words, failing to mention "dig", etc....)
And there's been cases where a place was never an issue or problem before. But when an whimsical "no" gets passed down, then that same person (who never gave the matter thought before, nor would ever have glanced twice at an md'r) , now all of the sudden starts booting others.
So .... be careful.