This happened to me during the housing test phase, kevbob turned up on my street in his guise of landscaper and fixed it quickly. I'm sure they will fix it as soon as they can, but the staff are busy at present.
Happened to me just now. I was in the process of restoring a Medium Herb Garden (gathering resources, actually) and came back to find that it had turned into a 16-plot regular garden. As several people had donated resources to help me, I'm reluctant to just remove it and imagine a fresh one.