Reference disappearing from inspector on Play

In my game I'm designing, I have my enemy controls referencing my score, which is a separate script attached to a separate object. I have the object reference set int the inspector and even in the prefabs, but when I attempt to play my scene, the reference shows "None." How can I alleviate this issue that I'm currently having? The code that I'm using to reference the separate script is in the update function of enemy controls. Also, I've attached some screenshots of the issue. Hopefully someone is able to help me out. The biggest issue is that this was NOT happening last night while I was working on it and suddenly, poof, my reference starts disappearing. Any help is much appreciated!

 playerScore = gameObject.GetComponent("Main_Score");

Before Playing Scene

After playing Scene