It was an unsigned order.

as the abortion had already been obtained and the issue will be revisited again, what was lost was a precedent

Cases do not get to the Supreme Court in 9 months.

“The decision is about the teen’s individual case and doesn’t affect an ongoing class-action case about the ability of immigrant teens in government custody to obtain abortions. The justices ruled in an unsigned opinion that vacating a lower court decision in favor of the teen, who had been in government custody after entering the country illegally, was the proper course because the case became moot after she obtained an abortion.”

https://apnews.com/1486c57e5a2540b1b6f13d0c520943c3

“The Supreme Court sent Jane Doe's case back to the U.S. Court of Appeals for the District of Columbia Circuit, with instructions for the district court that granted Doe an abortion to dismiss her claim as "moot," or irrelevant.”

https://www.dallasnews.com/news/courts/2018/06/04/supreme-court-vacates-decision-grant-jane-doe-abortion-months-after-already-one

“MCCAMMON: So this throws out that Court of Appeals order that forced the Trump administration to allow her to go forward with the abortion. But the reason that the court gives here is that it was a moot question since the young woman had already had the abortion by the time the case reached the court. So the court isn't really weighing in here on a lot of the legal nitty-gritty or the big, larger questions at stake, like whether an undocumented immigrant has the same right to an abortion as an American citizen, for example.”

https://www.npr.org/2018/06/04/616790106/supreme-court-throws-out-lower-court-ruling-on-undocumented-immigrants-and-abort

Here's some text from that actual article:

The upshot of Garza is that “when ‘a civil case from a court in the federal system . . . has become moot while on its way here,’ this Court’s ‘established practice’ is ‘to reverse or vacate the judgment below and remand with a direction to dismiss.'” In other words, because Doe’s abortion eliminated the controversy between Doe and the government — the Trump administration could no longer hold abortion patients prisoner to keep them from having an abortion if they are no longer pregnant — the case must be tossed out, along with the lower court decisions favoring people like Doe.

As a practical matter, this is not a sweeping victory for the Trump administration. A larger class action suit, which concerns a number of abortion patients similarly situated to Doe, will still move forward, and the lower courts may very well conclude that the government may not hold these patients prisoner to prevent them from obtaining abortions.