Per the WC Testimony of grounds keeper Emmit Hudson, the Signs were taken down and MOVED to a Different Location ON THE KNOLL! Those signs were still Physically On the Knoll when Hudson gave his WC Testimony.
What testimony are you talking about?
Mr. LIEBELER - There are two signs in picture No. 18, one says, "R.L. Thornton Freeway,
keep right." and the other one says, "Fort worth Turnpike, keep right."
Mr. HUDSON - There were two of them that wasn't too far apart right throught here - them
signs was - one was right along in here and the other one was either further up, I guess.
It's not in that picture - I don't believe."
As published in the Exhibits, the picture Hudson is being shown has limited resolution. The photograph view angle is similar to the better-quality photo below.
If you look closely, the Stemmons sign can just be distinguished from the foliage. Hudson viewing a less-defined photo would not be able to see the sign. You would think the groundskeeper would have kept track of the location where the Stemmons sign sat for many years and figured that the sign was obscured by foliage.
Mr. HUDSON - Now, they have moved some of those signs. They have moved the
R.L. Thornton Freeway sign and put up a Stemmons sign.
The dallasfreeways research presents evidence that the Thornton Fwy sign was replaced at its original site with a similar-sized sign topped by a smaller sign. This is based on a photo taken on the first-anniversary that included the new sign back-on. It is speculated that the new sign might have made referenced to both the Stemmons and Thornton Fwy, basically replacing two signs with one.
FWIW, these online images are claimed to have been taken June 4, 1964.
Blue Ribbon Commission - 56 Years On and Findings Still Valid