Line Segment Tool

Boy, this is either the most misunderstood tool Illustrator has, or maybe people just don't know what to look for. At any rate, we get constant directory searches for the subject. I thought it was pretty well covered in the Free Information page of the beanillustrator.com site. Guess not.

Here's what I can guess people are looking for:
Q • Can't see line segments.
A • A line segment is the path between two points. The first place to troubleshoot is to select the Selection tool (solid black arrow) and drag a box that encompasses the whole page. I'd say to drag over the area where you think the path is, but you may have changed the view in such a way that it's off the screen. So zoom all the way out and drag a selection. Another approach is to go to View>Outline (Cmd/Ctrl+Y). This takes all the colors and stroke weights away, and gives you a black and white view of all the elements on the page - even the invisible ones. If you go into the Outline view and see your path, it means that the Stroke has no color, or weight. You don't have to have anything selected for this suggestion. With either method, get back into Preview view (Cmd/Ctrl+Y), select the object that's been giving you fits and go to the Stroke palette (Cmd/Ctrl+F10) and see what the stroke weight is. If that box is blank, enter a point weight, or select one from the drop-down menu. If your object still doesn't have a stroke, then look at the Fill indicator at the bottom of the toolbar. Select a fill color from the Swatches palette, or create your own.

The only other instance I can think of that would cause this kind of problem would be that you have the artwork on a layer that has a dark color indicator that might be covering up a 0.5-pt or 0.25-pt stroke. That would only apply while you have the object selected, though.

Final thought: When you start to draw something, Illustrator uses the last fill and stroke that you used - you or the dude that keeps coming into your cube and messing with your computer. So if you had a drawing with a 3-pt stroke with an RGB color of R95, G254, B200, and a CMYK fill of C30, M14, Y55, K10, and started setting text you wouldn't notice anything (at least with the text). If you then selected the Rectangle tool to draw a circle (I'd send you home) and dragged out the rectangle, it would have that same stroke and fill color. The same is true if you've given the stroke and fill a color of None. When you start drawing again, you won't see your work. You have to keep an eye on the color indicator boxes at the bottom of the tool bar. At first, it may be confusing because you might want to change a fill color and just click a swatch only to find that the stoke changed color instead. That's the breaks - you either like it or get used to it! (My mom's philosophy about broccoli.)