The underlined words reveal that Devon has a big imagination.
Explanation:
The lines reveal that Devon is a big imaginative person. His behaviour is quite clear through his thoughts and his actions.
When Lara suspects that either the women (who was helping children on the skates) or the man (feeding pieces of bread to the pigeons) were prime suspects, Devon took it in another way. He deferred from Lara by saying that he thinks that someone might have taken it thoughtfully, to protect it from thieves. However, to find, who has taken it thoughtfully, he needs to ask questions to arrive at any conclusion.
These lines depict his imaginative nature.