[f. LOST ppl. a., after foundling.] A person or thing lost.

1

1872.  Raymond, Statist. Mines & Mining, 197. The great ‘lost river’ which bursts out of the vertical side of the cañon of the Snake—a torrent from the solid rock; a foundling rather than a lostling.

2

1898.  C. Benham, Fourth Napoleon, 24. Evidently she spent her existence on the look-out for the lostling.

3