You appear to have two tables: 1) The table where you use the value list to enter data and 2) The table that stores the data used to produce the value list.
Which table are you searching for the old values? To search 1), enter find mode, select one of the outdated values and perform a find. To search 2, create a new record in 1, select one of the old values, copy it to the clipboard. Switch to a layout based on the table for 2). Enter find mode, paste the copied text into the field that serves as the value source for your value list and perform the find.
If you can't find the data in either table, then either this is a custom values value list or something has gone wrong.