Correct Option (3)
The passage explicitly states in its concluding sentence that the toothbrush is carried to the railway station "wrapped up in my pocket-handkerchief". This directly indicates its final location.
Incorrect Options:
Option (1) "in his bag": The narrative details the protagonist's repeated failure to pack the toothbrush in the bag, indicating it is not its final location.
Option (2) "in his bed": The protagonist wakes up in bed after dreaming about the toothbrush, but the toothbrush itself is not stated to be in the bed.
Option (4) "lost": The passage concludes with the protagonist locating the toothbrush and carrying it, thus it is not lost.