I inadvertently deleted a number of contacts and sent them to "trash". How do I retrieve them?
Use the Advanced Search (in the Search menu) and check the box labeled 'Search in Trash (deleted contacts)'. It is a small check box in the Search Settings part of the Basic Criteria section. Whatever search you do will look in the 'Trash' rather than among active contacts.
Once those search results come up, you can select your desired contacts and, from the Actions list, 'restore' them.