You're not wrong. Per the Wikipedia article for A Day Without Rain, the album the song was lead single for;

> Following the 11 September 2001 attacks, sales of the album and its lead single, "Only Time", skyrocketed after it was used by several radio and television networks in their coverage and aftermath of the attacks.

And that was just from the article header. It's got an entire section about the 9/11 bump;

> Following the 11 September 2001 attacks, "Only Time" was used in radio and television coverage of the disaster, which led to increased sales and radio airplay of the single and A Day Without Rain, to the point of both records surpassing their initial peak on the US charts. CNN and ABC News, among other networks, played the song with "Fallen Embers" as backdrops of footage of the victims. Its position on the Billboard 200 climbed from No. 20 prior to the attacks to its all-time peak of No. 2, driven by the increased audience exposure of "Only Time". In the same month, "Only Time" reached No. 1 on the Billboard Adult Contemporary chart after it already spent 33 weeks on the chart, breaking a seven-year-old record for the longest climb to the top position in the chart's history. In November 2001, the single climbed to its peak of No. 10 on the Billboard Hot 100 chart, making it Enya's highest-charting single in the US. From October 2001 to January 2002, over 3 million RIAA-certified units of A Day Without Rain were sold in the US alone, which included a peak of one million copies sold in 19 days.

> "Only Time" gained further exposure following its use as a sound bed for promos of the comedy series Friends on the first five episodes of the eighth season. Following the media response and increased sales of Enya's records, "Only Time" was reissued as a maxi-CD on 20 November 2001 containing the S.A.F remix and original version, with earnings from its sales donated to the Uniform Firefighters Association's Widows' and Children's Fund in aid of families of fire fighters involved in the attack rescue operations.