Realistically, as somebody who hasn’t deeply looked into this but just read some reporting:
I doubt we’ve encountered any ET life. If we had, it’s even less likely we’d encounter it via crashed spacecraft. I fully believe ET life exists, but the probability of us being contacted by them is astronomically low.
Almost surely, our government is keeping some tech from us beyond our current understanding of what’s possible. I can’t imagine what it would be. Some sort of cloaking technology, something using quantum computing, etc. Some of the reporting on “alien” technology could have been related to this.
I also gather that some of the eyewitness evidence is from one or more fighter pilots, who regularly undergo Gs known to cause hallucinations. As a prior hallucinator, I promise these can be absolutely convincing. If not for all the evidence from other people around me not seeing what I was seeing, I would have completely believed what I saw, and even then I wasn’t completely convinced for a while.\
My son works in the “asteroid detection” project off of Uni of Wash. he’s a physics major and former lead data engineer at Amazon. Basically they get snapshots from various telescopes and satellites, mash them together, and check for any anomalous looking objects. They are concerned with just about anything of any size. From his descriptions, it’s hard for me to believe that there is no record in their data. They track stuff out quite a ways, and the granularity is always improving. Keeping the planet safe and all that.
And if any of you have read the SciFi novel “The Three Body Problem”, a trilogy about first contact, you are familiar with the phrase " The dark forest". This describes how alien Civ6 are most likely going to behave - like wild animals in a dark forest. Namely, you don’t want anything to know you exist. If it’s something lower than you on the food Chan, then they are the prey, you are the predator. Don’t alert the prey. If they are above you, then stay quiet and slink away. In either cas, don’t let others know you are there.
I found that an intriguing framework. Why would any alien civ break the rule of the Dark Forest? Sending out probes and shit is a bad strategy.
+++ it’s the best Sci Fi book I’ve read in the past 20 years. Lthough it’s a very small sample on my part. Here’s a link for those interested and who have the free time. Three body problem
And I read that the interstellar objects that have been identified were identified because of how fast they were traveling. Yet our probes seeking to go to places outside out solar system are traveling relatively very slowly.