Shares of Jack in the Box (JACK -1.24%) shed 11% of their value last week, after the burger flipper delivered ho-hum financial results. Jack in the Box posted a year-over-year decline in earnings from continuing operations. It is also now coming off of back-to-back quarters of missing Wall Street's profit targets.

Top-line growth isn't as scintillating as it used to be. Jack in the Box saw its revenue climb a mere 0.5% over the prior year's holiday quarter. This is the third period in a row of decelerating revenue growth, and you have to go back two summers to find the last time the restaurant chain was growing slower than it is right now.

There was weakness at its namesake chain, but the real surprise here is that Jack in the Box's Qdoba also failed to impress. Qdoba was initially seen as a big beneficiary of the health scare at Chipotle Mexican Grill (CMG 0.17%). Folks wanting to grab a burrito or Mexican bowl should have gravitated to the 674-unit chain as a substitute for Chipotle. 

It didn't happen. Systemwide comps rose just 1.8% at Qdoba, and the segment's operating income fell sharply.

Defenders of Jack in the Box can argue that Qdoba's comps soared 14% during the prior year's holiday quarter. It was going to be a tough comparison. However, with Chipotle's comparable-restaurant sales plummeting 14.6% during the quarter, one has to wonder where those defecting diners went. They didn't go to Qdoba, and that was with Jack in the Box dramatically ramping up its Qdoba advertising expenses.   

Jack in the Box even brought up Chipotle during Thursday night's earnings call. 

"We didn't see immediate changes in our sales that would tell us that there was a direct impact," CEO Leonard Comma revealed during the call.

To be fair, Jack in the Box also didn't experience a hit to its traffic as Chipotle got more aggressive in the market. Jack in the Box concedes that there must be some impact, but it hasn't been as pronounced as it's been for investors flocking to the chain that they expected to be growing briskly at Chipotle's expense. 

We know what the market thinks. Shares of Chipotle are trading higher this year, and Jack in the Box has shed 14% of its value. It's a strange situation, especially since negative comps at Chipotle continued through at least January. Customers clearly migrated from Chipotle since November, but we still don't have a firm gasp on where they went to fill their voracious appetites.