I am having this extreme problem with Blender where I have this character I am creating. The character uses a mirror modifier, and I am using Blender 2.83. I saved my file and restarted Blender and when I restarted Blender, some vertices and edges were not together and made it's own separate object.
What I Tried:
I tried everything with all joining of vertices with using the F key and all. I cannot find any answer on the web about this. I am just learning Blender, but I know that everything was together and I know I didn't press anything that could cause it so I desperately need help with this.
Image of what is should look like together:
Isn't actually together but what it should look like together.
This image below shows it together and should be connected with the whole surrounding, it worked before I restarted Blender.
Image when it is separated:
But once I restarted blender, it wasn't together like it is suppose to. I had trouble selecting the whole separate object but it still proves but point on how difficult it is when it is separate.
Also, while I already have this question written, how do I hide and show that selector mover thing, the green, red, and blue arrows one, I accidentally shown it but don't know how to hide it again. I do have some uses for it in the future hopefully but like to hide it in the mean time so it's out of the way.