AssetDatabase.IsMainAssetAtPathLoaded

Проверяет, загружен ли в память основной объект ассета на assetPath.

Все пути относятся к папке Project, например: "Assets/MyTextures/hello.png".

Дополнительные ресурсы: AssetDatabase.LoadMainAssetAtPath, Resources.UnloadAsset, EditorUtility.UnloadUnusedAssetsImmediate.

using UnityEditor;
using UnityEngine;

public class AssetDatabaseExamples : MonoBehaviour
{
    [MenuItem("AssetDatabase/Is Main Asset At Path Loaded")]
    static void IsMainAssetAtPathLoadedExample()
    {
        //Create a material and unload it
        var materialPath = "Assets/Materials/NewMat0.mat";
        var material = new Material(Shader.Find("Standard"));
        AssetDatabase.CreateAsset(material, materialPath);
        Resources.UnloadAsset(material);

        //This will be false
        Debug.Log(AssetDatabase.IsMainAssetAtPathLoaded(materialPath));
        //Load material into memory
        AssetDatabase.LoadAssetAtPath(materialPath, typeof(Object));
        //This will be true
        Debug.Log(AssetDatabase.IsMainAssetAtPathLoaded(materialPath));
    }
}