For any individual trucking firm in a liquid market served by several such firms, the driver market is in fact highly elastic. If this Swift Transportation company which is featured in the article wanted to avoid a 20% decline in their share price, they merely had to walk into the break room at the competing trucking company and offer $10,000 spot bonuses to switch companies. Boom. Elastic.
Anyway, Swift's annual report says that driver wages as a fraction of revenue have fallen in each of the last two years, so it's their own fault if they came up short on drivers.
According to the article, the shortage is industry wide. The result of what you suggest would be a bidding war for the existing truckers, until the point the bidding has devoured all economic profit. We don't see that happening, clearly.
My hypothesis of implicit or explicit collusion among the dwindling number of trucking firms to drive down wages instead of drawing on supposedly elastic supply manages to explain that, on the other hand. The only other possibility would be an industry wide miscalculation that just happens to look the same as widespread collusion.
Anyway, Swift's annual report says that driver wages as a fraction of revenue have fallen in each of the last two years, so it's their own fault if they came up short on drivers.