To answer Mark R's query - these signals are shown in most publications dealing with SAR and I imagine SAR pilots, and most pilots with professional experience, would at least realize that something noteworthy is happening down there. Amateur pilots, perhaps not so much. The signal of threes, whether fire, whistle blasts, or whatever is more commonly known, although your average hiker is probably unaware. At least you are making noise and someone will investigate..

SAR pilots might at least have reference material with them to decode the ground messages.

FAA pilot training does not include learning about SAR ground signals so the person flying the small airplane down low near the person in need of rescue is not required to know the signals. Chances are that in Alaska many pilots have a reference card but in the lower 48 - not likely.

The signals table is a good idea for those trained and proficient. But much like Morse code, it's only useful if both sides are trained and proficient. Nowadays US navaids don't always use Morse identifiers because Morse is now obscure.
Even for ham radio operators Morse is now not required learning.

So, has using "SOS" as an international distress signal become outmoded, along with Morse Code? Are there really that many fliers, sailors and other adventurous types out there who wouldn't recognize its meaning?

I gotta say, though, that I thought the resourceful lady's adding an "!" exclamation point after spelling out "HELP" was a nice finishing touch.

The other signals are easier to construct, but an SOS would be recognized.

The Boy Scout Wilderness Survival merit badge pamphlet includes some of those same signals as the SAR manuals. It is one of the requirements for them to construct them.

In my experience (which is by now a trifle dated), most people in trouble in the wild do not construct any signal -still a good idea, however.

I had a chat with a highly experienced pilot friend of mine. This guy has well over 4000 hours, mostly bush flying in Alaska, winter and summer. He said neither he, nor any other pilot he knows, is really all that familiar with the ground signals. He said he's seen the card somewhere or another, but doesn't really remember them, nor does he keep a card in his plane.

He pointed out that unless a pilot is flying in an organized search, he really isn't looking at the ground much, rather he is looking around for other aircraft. He also pointed out that a mirror flash, unless it is flashing in some recognizable pattern, might not be so good. A single flash is too easy for the pilot to think it is just the sun reflecting off of a puddle or something. And in Alaska, one can't count on having sunny days.

He also said that smoke and fire, the bigger the better, is probably the best way to get attention. He said that if you are going to spell something out on the ground, plain old "SOS" is probably best. It might be best to combine these. A smoke plume to catch the pilot's eye, and a big "SOS" to indicate you need help.

Will he take a reverse Z, square, and reverse Z?

On a tangent to the original posting...
The incident has piqued interest in wilderness survival courses.

http://www.cbs5az.com/story/31731548/crash-course-in-survival

And, no I don't think the Zombie Squad logo is going to help.
However, a big, orange, tarp with S.O.S. or HELP emblazoned on it should stand out like lipstick on the Michelangelo's Madonna of Bruges.

I would say it has prompted an individual "who knows a thing or two about survival" to toot his organization's horn. Somehow I suspect that outfit's philosophy might not align with that of ETS as shown by the following quote from the referenced website:

" With a well-educated and armed populace, any individual, group or country intending to do us harm will be met with great resistance. "

Plenty of us "know a thing or two about survival;" some of us might even know up to five or six things about survival. I will say that what I do know about survival did not come from my time in the military. I was surprised at the almost total neglect of that subject during my time fighting off our enemies....