Can you post a screenshot of Discover when you are searching for the field? Also, what type of field are you searching on? Is it analyzed?
One thing I can think of is if you are using an analyzed query on a non-analyzed field, the analyzed query would drop the "/"s but the non-analyzed field would retain them.
Or it's something much simpler like your time range is not encompassing your data span. Hence some screenshots would be helpful. Thanks!