Technically, it is entirely possible, at least slightly more than a 0% chance, that those letter were not put there by a person but washed up randomly. However, we could very easily conclude that they were put their by design, given the experimental examples that I used above. And the blatant probability that outliers are not the status quo
Now, the flip side of that is not what you think, however. It doesn't suddenly work in the reverse as a trap (meaning that what you're hoping to catch me saying or insinuating is that design is the more obvious precursor to study of the natural world)
If you are to assume that the existence of the cosmos, which has only every shown itself to be random via millions and billions of examples, is somehow different from being random, how would you support it?
Essentially, you're trying to make the argument that looking at the properly formed symbols, which spell out the word HELP, are obvious for design, thus the entirety of the world is evidence of design, you're just begging the question. This is no different than what Ray Comfort did in his epic fail of a debate on national television and what countless others have done before and after. (I just pick on Ray because he's easy. There are heavier hitters that have continually made the same mistake, and you yourself have admitted that you can't support design with evidence.)
This:
Based on the conclusions garnered from hundreds, possibly, thousands of other examples like it, can be quickly filed away as having been designed. The probability that the stone face was produced randomly would be irrational unless you have literally hundreds or thousands of contradictory examples to the former, showing how this could possibly be a random formation.
This:
However, has literally millions upon millions of examples supporting the deduction that it is a random occurrence. (Or would you look at this photo and point to the obvious design and fingerprint of an omniscient deity?) There are so many examples of these random formations, for example, that we even understand the variables and processes that shape them. We know, to a larger extent, what their formation entailed, based on scientific principles that were discovered before these things were even known to exist. Those very same scientific principles are used for predicting and studying other phenomena as well, all over the solar system, which match what we would expect to happen in a universe created by random processes.
If you're to argue, for example, that "sunsets are pretty therefore there must be a god" - then you have to likewise admit that there are far more numerous examples of that same designer being a complete dunce when it comes to all of the useless, random, crap that is just flying around in the darkness for no reason whatsoever...