By default Ultra Recall does not keyword digits, but this feature can easily be enabled at
Tools | Options | Import | Keyword words containing digits.
Note that you will need to re-sync/re-keyword items that were imported before this setting is changed (simply select the items and Synchronize).
Another option that can be used (without changing this setting and resyncing existing items) is to use the
Item Title or
Item Text as the attribute with a
Matches Wildcard *<number or phrase here>* as the search criteria (essentially an
Extended Phrase Search).
Note that use of the Item Text virtual attribute is inefficient and could result in a long-running search, it is recommended that a limited search be used with large databases.