I got downvoted instantly for this question:
Hostname from IP address (again ...)
Can anyone tell me what the problem is? If it is just noise for network professionals, and they are irritated by it, where else on Stack Exchange can I post a question of that character?
An ideal question that receives upvotes here will spell out a clear problem statement and show effort in researching that problem before posting here.
Most of your current question body focuses on figuring out the nature & host name of a machine you already identified as different from the one you are looking for because it did not present a matching host key. This smells of XY problem.
In fact, you appear to be looking for (a way to connect to) a machine you can positively identify by its manufacturer (one not very typical of the narrow scope of this site) or its host key (you say you simply deleted that, not very typical in the narrow scope of this site).
If you present your actual goal as the question to be answered, the question is more likely to be helpful to future readers, and more likely to be conclusively answerable - unlike the current state of the question, which pretty much stalls with a deferral to whatever stores host names in your network.
Then again, if you figured out that part and spent enough time in the nmap man page (a tool you already correctly identified as potentially helpful) you probably would not be asking at all, so do not interpret this as suggesting you have to figure out everything by yourself. Just try to make your question clear enough to be helpful to the audience of the site you are asking it on.
