Do you have a citation to that, and a link?
Google "Nevada State Constitution". It's in the first paragraph.
The Act of Congress Approved March Twenty First A.D. Eighteen Hundred and Sixty Four To enable the People of the Territory of Nevada to form a Constitution and State Government and for the admission of such State into the Union on an equal footing with the Original States, requires that the Members of the Convention for framing said Constitution shall, after Organization, on behalf of the people of said Territory, adopt the Constitution of the United States.Therefore, Be it Resolved, That the Members of this Convention, elected by the Authority of the aforesaid enabling Act of Congress, Assembled in Carson City the Capital of said Territory of Nevada, and immediately subsequent to its Organization, do adopt, on behalf of the people of said Territory the Constitution of the United States[.]
Sorry, I don't see them signing away said territory. Perhaps you can point it out and we'll discuss it?
I'm on my phone, so posting quotes is a pain in the ass. Look at the section titled "Ordinance" - specifically, the sentence after the word "Third".