Values in quotes when pasted in Notepad?

I have a shared document that several staff contribute to. There is a column for ID numbers, and another column that leverages these values for lookups. Sometimes the lookup will fail despite the ID appearing accurate and existing in the lookup table. Only when I paste the value into Notepad does the problem reveal itself:

Most IDs will come out as

12345

But the ones that fail will show as

“12345 ” 

This happens “silently” in Excel as I have not found a way to indicate when this has been done or if it is the reason for the failed lookup. When I find these, deleting the cell contents and re-keying it generally fixes it. I am not getting a “number stored as text” error or anything else. Is there a way to pick up on these more easily? I’m not sure what terms to search for to see what can be done as far as detection or data validation etc.