There are a couple of issues going on.
First, it is important for you to realize that questions asking for product or service recommendations are off-topic on this site, as well as most Stack Exchange sites. On this site, that is generally interpreted to include asking for recommendations on things like books, websites, and other educational materials. Your question specifically asks for a "resource (book or otherwise)," and so it was likely to get closed.
If you have a specific question about mortgages or even about something that you had read in the book you referenced, that would certainly be on-topic. But asking for a general "What books can you recommend to teach me X?" is off-topic.
Normally, questions that are off-topic are closed long before they are deleted. When this happens, a notice appears informing you the reason that your question was closed, and you would have the opportunity to respond via the comments or edit the question to try to bring it on-topic. Unfortunately, a moderator decided to delete your open question with no explanation. By doing this, he hid it from view, leaving you with no explanation, and has prevented you the opportunity to comment on or edit your question. Normally this is only done when rude or offensive language has been used, or in cases of spam. But those aren't the cases here, so I don't know why the moderator decided that this question was bad enough to warrant an instant delete, forgoing the normal closing process.
Sorry that this happened, but it is unlikely that the question could have been edited to bring it on-topic. If you have a specific question about the mortgage process, feel free to ask a new question.