Have I been “cheated” if termites continue to infest my home after treatment?

No. Unlike other services such as plumbing or electrical, termite control involves living creatures. The best treatments performed by knowledgeable firms can fail at times. Termites find their way through tiny, untreated gaps in the soil. The intent is to establish a continuous, impenetrable chemical barrier, this is all but impossible to achieve in actual practice.
In the case of baits, it may take several months for termites to find the below-ground stations. Several months more to achieve control.
 
The best thing to do is to make sure you have a contract that provides for treatment and repair if termites return. Renew the contract yearly. Also make sure to have the company do a annual inspection inside and out even if you have bait.