C# doesn't recognize some symbols

Question

I read strings from text file, and among the strings there is one: "15121 ♥☺020 000000/=n531☻".

I use .Contain() method to spot ♥☺☻ symbols in the string, but it doesn't recognize them. For ♥,☺,☻ I also tried \u2665, \u263a, \u263b (as arguments for .Contain()), but none of them were recognized. Moreover, I copied the string (from console output window) and pasted it into my code to compare symbols one by one.

string s = "15121 ♥☺020 000000/=n531☻"; // the same with "15121 \u2665\u263a020 000000/=n531\u263b"
for (int j = 0; j < s.Length; j++)
{
    Console.WriteLine($"{line[j]} == {s[j]}: {line[j].Equals(s[j])}");
}

This is what I got:

What may be wrong and how do I recognize those symbols?

UPDATE: The input file I read strings from is a usual text file, and the strings inside looks like these (txt opened in Notepad):

As you can see, there is THE string among the others.

I don't use any encoding when reading the txt, and to specify how I do read the file and what the line is, here is my code:

            string[] lines = File.ReadAllLines(path + target_file_name);
            var list = new List<string>(lines);
            for (int i = 0; i < list.Count; i++)
            {
                string line = list[i];
                if (line.Length > 21)
                {
                    Console.WriteLine(line);
                    if (line.Contains("/=n"))  //used just to catch THE string
                    {
                        var line_b = Encoding.Unicode.GetBytes(line);
                        Console.WriteLine($"{line_b} : line = {line}");
                        foreach (byte m in line_b)
                        {
                            Console.Write(m + " ");
                        }

                        string s = "AAXX 15121 ♥☺020 000000/=n531☻";
                        Console.WriteLine();
                        var s_b = Encoding.Unicode.GetBytes(s);
                        Console.WriteLine($"{s_b} : s = {s}");
                        foreach (byte n in s_b)
                        {
                            Console.Write(n + " ");
                        }
                        Console.WriteLine();

                        for (int j = 0; j < s.Length; j++)
                        {
                            Console.WriteLine($"{line[j]} == {s[j]}: {line[j].Equals(s[j])}");
                        }
                    }

Reading all the lines from txt and converting them to List is a must for me. Thus, the line is a string line from initial txt file.

I have dumped the bytes of the inout text string var b = Encoding.Unicode.GetBytes(line); and compare with my literal (@pm100), and here is the result. Not quite sure what it does give me:

I'm sorry, I'm not willing to publish my code, and I may not understand some of your suggestions for I'm not very proficient in C# (and coding in general). So I would appreciate any further help as it is, if possible.