I have to agree with KeyResults. It "only xxx feet to the cache" while in shorts and flipflops. I do beat the weeds or brush pretty vigorously with my walking stick. Usually have the same experience leaving the cache "Oh, THERE'S the trail!". Kayak caching is my favorite way to cache in the summer.
Asp was my first thought, too. I had a really bad encounter with one (some?) when I reached into a hole in an oak tree once. I immediate (it was in the boonies, so that meant 15 miles) drove to the nearest pharmacy for internal and topical Benedryl. Still, my arm was swollen and my glands too. Nothing nearly as bad as you experienced though! Hope you're better soon!