If you are in 'Management' - 'Group card' and are trying to search for a specific service group from a year ago, you might have an empty picture.
The reason for this is that the service group will disappear on the 'Group card', when the sows have the status as 'Lactating', 'Weaned' or 'Exit'.
You can, however, go to 'Sows/Boars' - 'Service' and add 'Service group' to your layout.
See this manual on how if in doubt: Add or remove columns from a layout
Go to the green filter line in the column 'Event date', right-click and choose 'Between...'
Choose the dates the service group was serviced and click 'Ok'
Now you can see the animals in the list.