I suspect this question has been answered before, but I couldn't find it in a search just now. I'm trying to draw on top of an imporrted bitmap (a jpg), and the lines/objects keep disappearing under the bitmap. Not all of them, and I can't figure out a pattern to it. I've drawn the lines on a separate layer as well as trying it on the same layer as the bitmap. I've tried playing with Layer Order in the Display menu as well as in Layer Manager. Typically, when I draw on top of the bitmap, the lines are visible until I hit Esc/Regen. Then SOME of them will disappear.
So far, I think Rex's reply is the one that works. Per the other suggestions, I've tried every variant of layer ordering and layer management, and none of them yield anything like a consistent result. The odd(er) part is the inconsistency. Sometimes entities on other layers will appear and sometimes they won't. Then they may re-appear after fiddling, only to disappear again. This happens even with objects on the same layer.
I've usually placed the bitmap's layer "below" the active-layer when drafting-over a bitmap. Often the line-color on the active-layer inverts in-contrast-with the bitmap below it. Also after zooming-in, I typical regen <shift-u> to reset the the display-list's screen-image to place the active-layer on-top-of the bitmap's layer.
One of the first things I do in any project is make sure "display-layer order" is set to "in order". That makes DataCAD to the regen in layer order sequence. Then I make sure that I insert any images on low-number layer ("top of the list"} so that they are put on screen first, and my work, especially my active layer, is drafted later, and always appears on top of the image.