The mortgage document should be recorded in the land records. However, whether the note is recorded depends on the practices in your particular state. In Massachusetts we only record the mortgage. In Connecticut the note is also recorded.
Therefore, first check the land records to see if the note was recorded. If it was, you can obtain a copy for a per page fee. If the note wasn't recorded then request a copy of the first 2 or 3 pages of the mortgage document and the notary page. (You would be specifically looking for the pages that recite the name of the mortgagors and mortgagee, the date, property address, loan number, dollar amount and the name of the notary.) The notary page might help the lender indentify where the mortgage originated. (Ordering a copy of the entire mortgage document is usually unnecessary at this point and can be expensive since land records offices may charge around $1 per page for copies.)
Send a written request for a copy of your note to the lender at the address recited in the mortgage. Attach copies of the mortgage pages you obtained to help the lender identify your loan file. Mail the request with delivery confirmation so you can confirm that your request was received by the lender. Keep a copy of what you sent along with proof of delivery.
Be aware that copies of the original notes are hard to obtain in many cases. Especially if your lender is a national mortgage giant or one of the giants that are no longer in existence. In many cases the original mortgage was immediately sold and bundled and resold many times. The original note is often lost in the process. If you borrowed from a local bank it should be much easier to obtain a copy of your note.