If you want to search a file by a number, always use the asterisk symbol ( * ) before and after the number. File names often contain underscores, which the system thinks is one word. Therefore, if you would search for a part of that word/phrase, please use the asterisk sign ( * ).
Please see the example: *1234*
However, if you are certain that your file name contains the numbers on their own like, for example, number 5678; you can skip using the asterisk symbol and you will get the following result: