My girl Ellie had Giardia when she was about 6 months old... She was having intestional isses for awhile.... so I took her to the vet.... they didn't find anything in her stool sample and gave her something to calm the colon down... which would help temporarily... . but then the poops would come back...
Ellie's dog friend at the apt complex we lived had been diagnosed with Giardia... So when Ellie went back to the vet, with yet another bought of the poops, I asked her to test for it... and sure enough she had caught giardia from her buddy... it is very contagious.... so it is possible Kuma could have Giardia and got it at the dog park.
After a course of antibiotics, Ellie was cured of Giardia... and she hasn't had it since.
Hope this info helps... and I hope Kuma feels better real soon!