Is there evidence that Rawle's book was "suppressed"? For one, I'm not sure how that could have happened, even if someone or some group wanted to.

Doing a quick search, I found a few references to Rawle's work spanning back nearly a century. For instance,

The Historical and Geneaological section of _The William and Mary Quarterly_
Vol. 20, No. 1 (Jul., 1911), 66, says:

"Secession Taught at West Point in 1832. Benjamin S. Ewell, who was chief of General Joseph E. Johnston's staff, was a cadet at West Point in 1832. In the College Library is a book, by William Rawle, of Pennsylvania, entitle "A View of the Constitution of the United States" in which is written on a fly leaf, "1832 Cadet Benjamin S. Ewell, West Point." In this work the right of a state peaceably to withrdaw from the Union is strongly maintained."

In 1920, Walter Fleming wrote an article entitled, "Some Documents Relating to Jefferson Davis at West Point" (_The Mississippi Valley Historical Review_, Vol. 7, No. 2 (Sep., 1920), pp. 146-152) which records:

"There has been some controversy as to the use of Rawle, _View of the constitution_, as a text at West Point in the time of Davis. Rawle held strongly the doctirnes of state sovereignty and secession. After the civil war, when Davis was charged with treason, his lawyers proposed to offer the book in evidence when the case came to trial. It is not yet certain whether Davis studied Rawle or Kent." (Fleming, 151-152)

The use of Rawle's book at West Point is also mentioned in James A. B. Sherer, _Cotton as a World Power_ (New York: Frederick A. Stokes, 1916), 251 and Charles Francis Adams, _Studies Military and Diplomatic, 1775-1865_ (New York: The MacMillan Company, 1911), 340.

The most famous reference to Rawle's book, though, was by James Latta in his article, "Was Secession Taught at West Point," 1909.

With this information available, I'm not sure how Rawle's work could have been hidden or suppressed.