A mistake like that is from pure carelessness. I would call the offending company and ask to be compensated for your loss. There is no reason why a yard would be mis-applied. There could be serious legal issues form a lawn application on a non customer yard. I had an applicator apply Pre-E and Herbicide to the wrong address. The homeowners were card carry members of the Sierra Club and the issue turned ugly. As a company we were very responsive and apologizing but the homeowners call state and federal authorities. The miss treated lawn measured 5500 sq ft. When the dust settled and cooler heads (homeowner) prevailed I had to perform the following. 1- Mow the yard and remove clippings for 12 weeks. Length of residual based off of label for the Pre-E. 2- Remove all soil to a depth of 4 inches in organic garden. Fert-Pre-E prills found in garden. Replace with new organic mix top soil approximately 10 yards. 3- Replace all the plants within the garden 4- Buy the homeowner a new pair of Leather Keds shoes because she had to walk across her lawn. The other issue we faced was the lady just found out she was pregnant and her husband said, " if there is a miscarriage you might hear from our attorney." All that headache was generated by a employee who was careless and not paying attention. Talking with an State Ag inspector he said they could have taken me to the cleaners so do all I can to make it right. A very serious violation especially when you get a phone call from the EPA. In your situation only straight fert was applied so you dodged a bullet. Just something to think about and talk with your employees during a quick training session.