Kept 'returned'? That is what followed. The caretaker's part was recognising it. 'Junk shop' is where he saw it, not what he did.
Every word, accounted for
Theglue. never in the answer
stolenthe reason it is news. stays
schoolsays whose piano. stays
pianothe thing itself. stays
wasglue. never in the answer
returnedthe result. the caretaker never carried it back
becauseglue. never in the answer
aglue. never in the answer
caretakerwho did it. stays
recognisedwhat the caretaker did. stays
itglue. never in the answer
inglue. never in the answer
aglue. never in the answer
junkwhere he saw it. not what he did
shopthe place, not the news