As someone who has long since lost count of how many magazine bike shoots he has been involved in*, I can tell you that the usual method is as per Nikki's answer (first response in the thread). Ideally, you grab hold of the bike again before it topples over... but it doesn't always work out like that. As long as you can find a reasonably level patch of ground, it will tend to say upright for as much as a couple of seconds before gravity takes over, much like Wile E Coyote hangs in the air for a few moments before realising he has just run off the edge of a cliff.
Photoshopping a stand out of the pic seems like more work than is necessary when you can usually get good results without it. I have been on shoots where a stand is used and photoshopped out afterwards, but it's not common IME. I have also been on shoots where the bike is photographed on a matte and the background is photoshopped in afterwards but the results are never quite the same - you can nearly always tell. Sometimes photographers will make a composite of more than one picture, but usually this is for lighting reasons (eg one shot with lighting focused on the front of the bike, another shot with the lighting focused on the rear end).
We have a checklist of rules for positioning bikes in shoots (valves at 6 o'clock, cranks horizontal etc) but you have to remember to reset the bike after every shot, and then the designer goes and chooses a pic where nothing was lined up properly anyway and twerps on the internet accuse you of being an amateur... grrr!
*usually in the role of the person letting go of the bike and moving out of shot very quickly