Haha!

I've checked your AH.FM link, and there's indeed a rather typical English-language joke behind it.
No, as far as I can tell, **โThere's an owl for thatโ** isn't a traditional American saying. It appears to be a humorous variation on a particularly famous American advertising slogan:
**There's an app for that.**
In other words: there's an app available for that particular purpose.
Apple made this expression famous in 2009 through its advertising for the iPhone and the App Store. The slogan became so popular that people started coming up with all sorts of amusing variations on it.
*WIRED*
+1
### What's happening in your AH.FM thread?
I've looked at post #29 by robejaegs.
In that post, robejaegs responds to a message from Pavol_CH containing a sad GIF.
His reply is:
**there's an owl for that

**
A loose translation would be:
**We've got an owl for that!**
It sounds as though he's playfully referring to an owl as a response to that sad image. Whether there's a particular owl GIF or an earlier forum joke behind it is something I can't establish from this post alone.
*AH.FM*
The similarity to Apple's slogan is striking, but I can't prove that robejaegs is deliberately referring to it.
In short: probably a play on words rather than an established American saying. And it's precisely because he uses the familiar sentence structure, replacing *app* with *owl*, that it sounds amusing and familiar to English speakers.