It's almost impossible to find ANY of his reports to his superiors about UFOs, but that's also true about Walker, Sarbacher and all the rest of the scientists who worked on these early investigations. We know for a fact that they did, but there's virtually no written record of what they did, at least nothing that's available to the public.
There's nothing in the official record that LaPaz was ever in Roswell, and in fact there's nothing in it at all except the stuff about Project Mogul, the Blanchard pres release and the FBI memo. There's not even a document that anyone ever visited the crash site for any reason, whether to find a balloon or anything else, although we know that people were there.
People often complain that the UFO field relies only on eyewitness testimony, but part of the problem is that so many "official" records are obviously being withheld that often we would never know anything at all without the witnesses.