hole in Riv's head

Hey! Jasper Here! Mommy went on a long bike trip WITHOUT US! Can you imagine? Something called RAGBRAI and it sounds like SO MUCH FUN! Even though I really don't get the bike thing, mommy said there is lots of food and lots of people and even a few other dogs. I don't know why she did not bring me and Riv! I would have gone! I would do anything! I love everything! But we got to stay home with Daddy and he give us whole treats not half treats like Mommy so it was ok.
Anyways, when she got home me and River did our usual welcome, which means we ran straight at her, jumped up and down, circled, licked, sniffed, jumped some more, wrestled each other and then each picked up a toy and did a few laps around the furniture, like 30 laps, at full speed.
After we finished doing our welcome home laps around the furniture, Mommy was petting River and she said "OH YUCK." SOMEHOW, while she was gone, River got two big holes on the top of his head! There are two big holes and NO ONE is telling what happened especially not me. Here is a picture of the biggest one, and this is 5 days after Mommy came home and cleaned it out. Do you think his hair will ever grow back? See Mommy, you should not go away for so long!