As I've said before(:D) we have 2 smooth vizslas and they have been confused with anything from a whippet, ridgeback, weimaraner, long-legged dachshund(not us personally but have heard it from someone else!)irish setter(?!)and even a cross breed!! But as JG has pointed out any breed can suffer from limp, maybe the dog had a thorn or piece of grit in it's paw?
Hope this helps
Emily :)