Unless you're buying locally caught Salmon at a fish market, it was almost certainly flash frozen. Even if it's not frozen anymore when presented in the store.
Sushi grade fish is flash frozen at -40°f - not all fish is frozen this way. Most [0] sushi grade fish in the US is frozen this way before distribution. This is not the case for ALL fish. It would almost certainly have been frozen, just not necessarily flash frozen with the intent to distribute as sushi grade.
Most fish you buy will have a warning specifically saying not to eat it raw if it wasn’t frozen safely in this manner.
Most fish you buy will have a warning specifically saying not to eat it raw if it wasn’t frozen safely in this manner.
[0] http://factmyth.com/factoids/most-sushi-is-previously-frozen...