I recently heard an expert speak about fingerprints and it was really eye-opening as to what surfaces are best for prints and how fragile they can be. Basically, there are three types of prints: impression (imagine the three dimensional print left behind if you pressed your finger into a soft, moldable surface like clay or wax), patent (visible prints - imagine a finger coated in blood that pressed against a windowpane), or latent (invisible to the naked eye - these are left behind because the ridges of your fingers, palms, and soles of your feet have organic oils and sweat that can be invisibly left on certain surfaces). Because these latent prints are just made up of oils from your skin, on any surface they will break down over time and on certain surfaces they can be extremely fragile.
Forensic examiners classify surfaces in three ways - porous, non-porous and semi-porous. Porous surfaces are absorbent and would be materials like paper, cardboard, untreated wood, money, etc. Fingerprints deposited onto this type of surface are considered pretty durable and there is a high probability of collecting them, especially if the surface is smooth and non-textured. Non-porous surfaces , especially if smooth and non-textured, are also conducive for the deposition of prints, but because they do not absorb the oils and actually repel the moisture from a print as it's deposited, prints from these surfaces are more fragile and can be easily damaged by environmental factors (precipitation, heat, etc). These surfaces are glass, metal, plastics, painted wood, and rubber, for example. Semi-porous surfaces would be things like cellophane, glossy paper or treated cardboard/wood. This type of surface has to be processed using techniques adapted for both porous and non-porous surfaces. As with the other two types of surfaces, texture is a problem for print recovery because textured surfaces do not allow complete contact between the ridges of the skin and the surface being touched.
Some additional factors - surfaces that have become wet can be particularly challenging and require special techniques. Surfaces that themselves already have grease or oil are not great for the deposition of prints (some parts of firearms and human skin would be examples of this - in addition, human skin is not rigid and deforms under pressure so this can obscure print detail). Can you still get prints from these challenging surfaces? Yes, sometimes - but the probability is low and the detail, even if you succeed, is often not good enough for comparison.
TL said in the HLN special that they had evidence "suggestive" of a print but they did not know if it was the murderer's print. So we don't know if that was a patent (visible) or latent (invisible) print but it sounds as if it was perhaps not in the best condition when recovered or maybe a partial.
Here's more info about latent prints that covers what I shared above:
https://dofs-gbi.georgia.gov/document/publication/180850381gbi-latentprintspdf/download
https://dofs-gbi.georgia.gov/document/publication/180850381gbi-latentprintspdf/download