To answer your questions, the apron has remained within the Stiles family since 1836. There is no evidence that it came from anyone other than John Stiles, and they have politely but firmly declined my offer to have it displayed at The Alamo.
And apparently no proof that it did. Seventy years ago the Stiles Family was claiming their revolutionary ancestor was a johnny-come-lately to the San Jacinto battle, that Gen. Houston knew him by name and placed Gen. Santa Anna under his control. They also stated that "some tradition" claims a masonic apron or regalia belonging to Santa Anna fell into John Stiles' hands at the time, but we know this is impossible since Capt. Becknell's company was not enlisted yet and Mr. Stiles was still in northern Texas. In my opinion this throws a few loose threads into the whole apron story even though it has been up-dated for masonic and internet consumption.
Evidence of the disproportionate percentage of Master Masons assigned guard duty can be found in Carter's book, it is well-researched and well-written.
Where did Gen. Houston or any other contemporary masonic commander state that this was a requirement for guarding Santa Anna? Perhaps they were just looking for unbiased or honest soldiers to do their duty. Can I assume that James A. Sylvestor's Santa Anna capture party (w/ Joel W. Robison, Alfred H. Miles, Joseph Vermillion, Thompson, Cole and Mason) and Santa Anna's Washington D.C. escort (George W. Hockley, William H. Patton, Bernard E. Bee and Rueben Potter) are included as guards and the majority were masons? I don't have this book.
As for the Stiles family story changing, I can only speak to the conversation I had with Lewis Stiles' father Lester some nine years ago. He spoke about his ancestor being in Columbia in October 1836, and having no evidence in my possession of anything contrary to that, I took him for his word.
It's perplexing how a simple story can change so drastically without the infusion of new-found contemporary and primary information. Interpretation sometimes comes into play with these little-known family accounts and distorts the kernals of truth within. Initially Capt. William Patton and his Columbia Company was given as the protector of Santa Anna after the San Jacinto battle, which seems corroborated by Capt. Patton's taking Santa Anna all the way to the Whitehouse to see President Jackson. Since John Stiles didn't get the masonic apron at the San Jacinto battlground, I wonder what evidence implies he was in town to obtain it at Columbia in October. Pvt. Stiles was one of the rangers that was left at Nacogdoches on Aug. 31st, when the remainder of Capt. William Becknell's company moved forward. While some were on sick call/ duty and others were AWOL, Stiles apparently had severe equipment problems. Stiles was one of a few rangers that seems to have been left in camp because he had no, horse, rifle, blanket or equipment that was valued by his commander. Isaiah D. Lawson (Stiles companion and alleged Santa Anna guard) was in a similiar situation although he had a $90 horse. It's hard to perform great historical and military deeds when you lack transportation, weapons and a few dollars in your pocket, but many people have been placed in this situation.
Authentic or not, it's an interesting item, and even many Masons are surprised when they learn that freemasonry was rampant throughout Latin America (and still continues as such.)
I agree it's an interesting tale, but probably not for the same reasons. Freemasonry has played a big role in world history, but so have many institutions and there are always surprises.