This is the 17751st most frequent Polish word.
zostawiliśmy
"We left" or "we have left."
The word 'zostawiliśmy' is used to indicate that the subject, we, has left something (the book) at a specific location in the past.
Zostawiliśmy naszą książkę na stole.
We left our book on the table.
Here, 'zostawiliśmy' reflects the act performed by 'we' of leaving something (the drawing) for someone (the friend) in the past.
Na pamiątkę zostawiliśmy rysunek przyjacielowi.
As a souvenir, we left a drawing for a friend.
The verb 'zostawiliśmy' illustrates the action of 'we' placing or leaving an object (the message) in a specific location (the shelter) at a previous time.