FEMA had conducted a preliminary, very limited investigation of the collapses of all three WTC towers on 9/11. In Appendix C they discuss "two structural steel members with unusual erosion patterns were observed in the WTC debris field." In their conclusion, they stated:
"The severe corrosion and subsequent erosion of Samples 1 and 2 are a very unusual event. No clear explanation for the source of the sulfur has been identified. The rate of corrosion is also unknown. It is possible that this is the result of long-term heating in the ground following the collapse of the buildings. It is also possible that the phenomenon started prior to collapse and accelerated the weakening of the steel structure. [My emphasis] A detailed study into the mechanisms of this phenomenon is needed to determine what risk, if any, is presented to existing steel structures exposed to severe and long-burning fires."
FEMA makes clear that they had found samples of structural steel from WTC1 or 2 and from WTC7, and that they did not know if these samples "accelerated the weakening of the steel structure" prior to collapse. In other words, FEMA had uncovered what may have been relevant evidence in an explanation of the collapses of the WTC buildings. A proper investigation would have tried to determine what caused the corrosion of these samples, when it occurred, and whether it accelerated the weakening of the steel structures prior to collapse.
What sort of investigation did NIST perform relevant to these samples? None whatsoever. Zip. Zero. Nada.
Someone does not need to be an expert to see that NIST's failure to investigate what caused the corrosion of FEMA's steel samples is an example of ignoring relevant evidence.
Professional engineer Jonathan Cole did conduct experiments related to FEMA's samples. The first involved an attempt to reproduce it using materials that would have been present in a normal office fire: 9/11 Experiments: The Mysterious Eutectic Steel, but Cole was unable to produce similar samples:
However, when Cole performed his 9/11 Experiments: The Great Thermate Debate, by using thermate he was able to produce samples that looked eerily similar to FEMA's samples:
No microscopic or metallurgic analysis has been done of Cole's samples, but his experiments are far more than anything NIST was willing to do to solve the mystery of FEMA's corroded steel. A person would need to be willfully blind to complain that a layperson has no reason to doubt that the NIST's official investigation included all the relevant evidence.