Could not be reached for comment
Consider the statement in a news-article:
"A Dell spokesperson could not be reached for comment."
snipped from the article "Dell launches low-cost PC in China " (at http://www.infoworld.com/article/07/03/21/HNdelllowcostpcchina_1.html).
This is plainly incorrect, for in any reasonable universe, it will always have been possible to reach a Dell spokesperson.
Consider an expedition to locate an incarnadine unicorn. It's possible one may not find one such a beast, and one may said that "a unicorn was not found". One may not say "a unicorn could not be found", for it's quite possible that a herd (or appropriate collective noun) of unicorns was grazing across the street, the vista blocked by a giant hoarding. Hence a unicorn could indeed be found, even though it was not.
For "could not be" implies that a unicorn cannot exist (or rather, could not have existed). My thesis is that a unicorn can exist, and Dell spokespersons can be reached.
This is not pedantry, but an insistence upon truth (or upon the desire for truth).
The statement "A Dell spokesperson could not be reached for comment." reeks of perfidy. My brother mislaid the phonebook, and so I couldn't find Dell's number. I called Dell, but they put me on hold for three whole minutes and I lost patience. I was busy finding my grill for summer. Dell was too busy. Dell didn't give me a free T-shirt and a return ticket to Hawaii. Dell is not obliged to answer everyone who calls or writes to them. I failed to get a response from Dell, and went ahead with my piece anyway, as I don't get paid if I don't publish. The hotel where I was staying had a problem with their switchboard, and kept routing me to a pizza delivery firm in Lisbon, instead of to the Dell customer relations number.
One can accept this sort of thing only if a reasonable attempt was made, over a reasonable period of time. However, this is very subjective, and unless this information is also provided alongwith the article, I suggest the path of greatest truth be taken, and "could not" in such cases be replaced by a "was not". If Dell was contacted, and they refused, then one may state that. As long as the journalist realizes that this refusal is no great assault against freedom of speech, or any civil liberty; on the contrary, it is the exercise of freedom. The freedom to refuse contact with the distasteful, or impertinent - or merely because one chooses so.