Which component blew up and needs to be replaced?

After replacing the battery in my Sansa Clip+ everything seemed normal – turned on, navigation worked, radio playback was working – but when I tried to charge it I smelled a magic smoke. Once opened, I noticed a component that blew up. Don't know if I messed up with soldering job and shorted GND lead from battery to the test pad nearby, or I accidentally shorted Audio Jack pad to smth nearby – will redo both after replacing the faulted component.

Interesting to know why it blew up. Was it just my bad solder job? Or was it caused by a cable / charger supplying more current than the player circuit can handle? Or is it (a wild idea) prone to aging and it was first-time charging in the last 5 years?

Now I obviously need to know to replace it with... something. According to the Rockbox wiki photo this component has a marking "S21" with a white stripe on one of its leads. Is it a diode of some sort? Which replacements I can order in EU?