It seems that the OP believes that
The concert's sold out
is the contracted form of The concert was sold out. It is not. It is the contracted form of the present perfect construction: Noun + has sold out or Noun + is sold out:
Google does indeed have results for “concert's sold out”
- Our concert's sold out but we're open late till 9pm that night with the @craftyfoxmarket plus workshops, DJs and bar!
- Our concert's sold out today at 2pm in the town hall
- I glanced around the deserted 'Park' and added, “Looks like this concert's sold out, and its Standing Room Only.”
- Hey, do you know if that concert's sold out?
- “Sorry, the concert's sold out. Maybe you can get tickets for a later performance.”
Other examples of present perfect contracted form:
- I've just bought a new car (I have just bought...)
- He applied to XYZ university and he's got the letter of confirmation that he's been accepted. (... he has got ... he has been ...)
The next example
Bob's a dog
Is the contracted form of Bob is a dog, a native speaker will not think that it means Bog has a dog, unless context tells us otherwise. In speech a person might get away with this:
My children keep all sorts of pets: Carol's a parrot, Anne's a rabbit, Tim's a frog, and Bob's a dog.
But as soon as you read that sentence, it looks weird: Carol is a parrot, and Anne is a rabbit. British English native speakers will most likely add got to reinforce the idea of possession, as in:
“Bob's got a dog.”