My dog ran away, came back tired and acting strange. What to do?

Hi and thanks for using Petco Pet Education Center, formerly Petcoach! Sorry to hear that but this could just be exhaustion and normal tiredness. They may have been exhibiting breeding behavior if they are male and female dogs resulting in exhaustion or just very tired from roaming while away from your home. I wouldn't encourage any playing. Let them rest up. As long as your dog is eating, drinking and going to the bathroom normally then I wouldn't be too concerned but if any seems different, the best bet is to have your veterinarian evaluate them. They can perform a physical exam, take their temperature, and advise any tests (fecal, blood, xrays, ultrasound, etc) which would help them with a diagnosis. Or they may just prescribe some medication if that is indicated. Good luck with your dog and I hope things return to normal soon.