Goblin Matron
Creature — Goblin
When this creature enters, you may search your library for a Goblin card, reveal that card, put it into your hand, then shuffle.
Wizard of Barge
Secret Lair Drop (SLD)
• #1312★Rulings
If an effect refers to a “[subtype] spell” or “[subtype] card,” it refers only to a spell or card that has that subtype. For example, Goblin War Party is a card that references and creates Goblins, but it isn't a Goblin card.
(wotc • 2019-06-14)
Because the “search” requires you to find a card with certain characteristics, you don't have to find the card if you don't want to.
(wotc • 2004-10-04)
Rulings
If an effect refers to a “[subtype] spell” or “[subtype] card,” it refers only to a spell or card that has that subtype. For example, Goblin War Party is a card that references and creates Goblins, but it isn't a Goblin card.
(wotc • 2019-06-14)
Because the “search” requires you to find a card with certain characteristics, you don't have to find the card if you don't want to.
(wotc • 2004-10-04)