Thank you for all the responses!
My coop is not locked, the door is always open, it is also made of chicken wire, which means I can see in at all times.
As for seeing my chickens before they see me, I just look out the window and I can see them outside of the coop standing all together.
The reason they stop crowing when I go outside is usually because I'm yelling at them as I open the door

Or I bang on the window in the hopes that I won't have to go outside, so they know I'm coming.
I can't see any signs of an attack and there are definitely no traces of predator's that I've seen!
But by the time I get outside when the sun is up, the chickens have usually dug up their enclosed area, so any signs of a threat would have disappeared.
I'll keep an eye out and report anything.