This account was posted on 1/12, so it is probably referring to that day:

Translation:

Today OP saw Changmin and Siwon at sum cafe cheongdam. No pix allowed. Seems were w staff? trainees? quite a number of people as they seemed to be asking after each other and picked up hot americano and white? yoghurt smoothie before leaving.

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Credits:

@dyodyoheart,
Translated by @snxy,
Shared by TVXQ! Express