I had somewhat of the same thing happen to me a month ago... my GSP's got loose in the heat of the day. When they came back home everything seemed fine but the next day my girlfriend called telling me that one of my dogs could stand up and would loose his balance when he went to eat.I raced home and took him right to the vet.......after testing him from everything under the sun my vet was stumped.....she took a stool sample...a blood test...head to toe examination...
Right before we left she picked up his foot and immediatly saw the problem.His pads had been burned off by the hot asphault in the heat of the day.It took two weeks and lots of antibacterial numbing cream to get both dogs healed! It was very painful for my dogs and myself.