This is one of those 'who knows' scenarios that unfortunately is difficult to prove. On the one hand you shared your work with producers who you imply may or may not have shared some ideas of your original work. On the other hand you can't really be sure if they did that - is that the crux of it? Did you leave your screenplay with them, or did you just pitch your concept?

Here's an interesting article you should read:
https://scriptshadow.net/did-someone-steal-your-script/

A few years ago I had a screenplay of mine stolen and passed off as someone else's. Turned out okay, though, but there is no doubt in my mind that shady shit goes on like this all the time. Like Libby said, difficult to prove, but I'd say you have a valid concern.

Steve

It is not impossible, but highly unlikely I would say. A long time has passed since you sent the screenplay.

"Producer connected to the agency who is connected to an individual who later influenced the project" - 6 degrees of separation. Much less when you are talking about a specific industry.

65 features aliens who visit Earth at the time of the dinosaurs. I am utterly shocked it hasn't been done before. It's certainly no stretch that two people, twenty years apart have come up with similar ideas.

Spacecraft getting into trouble in space and crash landing is a trope, so very common.

The bug - Smacking a bug on the back of your neck is no where near niche enough to warrant suspicion. especially given where they are.

Visual aids from high vantage points - Yeah, same as above. Many movies do it, and it just makes logical sense.

The Meteor finale - This is a historical event, and not something fictional unique to your screenplay. It also makes perfect sense that someone telling this kind of story would use the meteor for plot.

I've obviously not read your screenplay. but just based off what you have said, it's not impossible they used your original screenplay as a basis, but I find it extremely unlikely.