Suspicious activity

We have always made sure that our house and back yard are secure and our dogs are safe.  I received a call from a neighbor on Mezes that he found my dog running loose and we're grateful he found him. 

With that said, after I picked up my dog and returned home, I checked every possible escape route, and found none. we've never had this happen before, and can only assume that someone may have tried to access the backyard but was stopped when confronted by our German shepherd. We may want to keep an eye out for suspicious activity.