[koheripbal]

Correct. The ability to infer this from observational data was only possible with the technique pioneered in this paper.

Remember that we cannot even see exo-planets visually (with one or two very nearby exceptions).

[svachalek]

According to Wikipedia, there are not even any confirmed exomoons yet. So it's interesting that a disk was observed first, although given size/brightness that's probably not a surprising result.