It's been a rough few months for telecommunications giant AT&T (NYSE:T). Its share price has declined significantly over the past several weeks, as investors have become frustrated with the company's lack of growth. Telecom companies such as AT&T and Verizon Communications (NYSE:VZ) are counted on for their hefty dividend yields. Underlying growth can be hard to come by, however, due to the high level of costs in the industry.

Shares of AT&T declined again after releasing fourth-quarter and full-year earnings, and now languish near a 52-week low. Despite another round of earnings that produced little growth, AT&T still has a significant growth opportunity, which would be to acquire European telecom giant Vodafone (NASDAQ:VOD). That's what investors should focus on in the months ahead.

AT&T's earnings takeaways
AT&T actually had a solid fourth-quarter and a very profitable 2013. Adjusted earnings, which strip out one-time items, increased 20% in the fourth quarter and 8% for the full fiscal year. Revenue increased nearly 2% in the fourth quarter, driven primarily by subscriber growth. AT&T added more than 2 million new wireless and wireline high speed broadband connections in the fourth quarter.

Not surprisingly, AT&T's wireless segment led the way in the fourth quarter. Its wireless service revenue increased nearly 5% year over year. Wireless data revenue jumped 17% versus the same quarter last year. AT&T added 1.2 million new postpaid smartphones in the quarter, and smartphones accounted for a record 93% of postpaid phone sales.

By most metrics, AT&T had a very solid quarter and full year. The company was profitable and continued to do what it does best: returning loads of cash to shareholders. AT&T returned nearly $23 billion to shareholders in the form of share repurchases and dividends in 2013.

A major catalyst for future growth
Investors might be understandably frustrated at the lack of growth in the telecommunications industry. However, there are still viable avenues for AT&T to keep growing, the most prominent of which would be acquiring Vodafone. AT&T recently issued a statement saying the company isn't interested in an acquisition, but investors shouldn't be fooled: the deal is very much in play.

AT&T stated it would not initiate a bid for Vodafone over the next six months. It can still respond to an offer initiated by Vodafone, or make a bid in response to an offer by another company. In fact, AT&T issued the statement simply in response to a British regulator seeking to prevent merger speculation. It's likely that AT&T is still interested in Vodafone, and for good reason.

Vodafone sold its 45% stake in Verizon Wireless last year to Verizon Communications for $130 billion. The deal obviously made sense for Verizon, since it now has the advantage of bringing in the remainder of its highly profitable wireless business that it didn't already own.

Even though Vodafone's stake in Verizon Wireless is off the table, Vodafone still holds valuable assets that would be extremely useful for AT&T. Vodafone's emerging market assets are performing very strongly. Vodafone is performing fairly poorly in Europe, but its Africa, Middle East, and Asia Pacific (AMAP) segment is growing strongly. Vodafone's total service revenue fell 5% in the most recent six-month period, but its AMAP division grew revenue by 6%.

Bottom line: AT&T is still a growing company
While the market seemed disappointed by AT&T's results, it's worth noting that the company still grew in 2013. AT&T showed growth in nearly all of the metrics important for a telecommunications company: namely revenue, earnings, and subscribers.

Plus, a hidden catalyst for future growth remains in the form of a Vodafone deal. AT&T can't initiate an offer over the next six months, but that doesn't mean the deal is dead by any means. Going forward, investors should carefully monitor anything AT&T has to say about a possible Vodafone acquisition.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.