You can't usually select elements based on their geometry (ie. the way they were placed). The only way you can select this text is if one of it's other attributes are different that other texts, such as pen color, layer, font, hotlinked module, font size, style, alignment, leading. None of which refer to the text's angle.
The only suggestion I have is to select all the angled texts and change their color. At least then you could select them more easily in the future.