Sounds like the pesticide may have been an insecticide, not an herbicide, unless, maybe the herbicide was specifically a crab grass killer - that would probably leave the flowers and your hops alone.
Sometimes I wonder about pesticide applicators. I have no problem with most pesticides (fungicides, insecticides, herbicides, acaricides, etc - PSA - please reserve the use of pesticide when you are talking generally about all of them - don't say pesticide, when you only are refering to one specific class, it can lead to confusion). Many of the problems that do arise are due to applicator error. I had to go to my every 5 yr pesticide safety review last week and it is amazing what some people do.