Is this normal? Applied for a govt job and they offered me something completely different

I applied for a contract job at one of the government offices in a certain field and they gave me an offer at the place but for a completely unrelated field after one interview, without any communication on doing so. For example, if I were in medicine, it's like being a face doctor and they gave me a job in podiatry. Is this normal? I assumed if I apply to job X and I'm told I have an offer, that it would be for job X.