The temp. screens were extra long and you closed the doors over the ends, I have got one in the garage, it saved my sister an unpleasant journey in the wet once, so they do work, even the wipers work after a fashion on them. I expect it would crack up if I unrolled it now, but in the days before laminated screens were on everything they were very useful.
No, no screen is not a failure. I used to get my kit car mot'd without a screen and put it back on immediately after (minor crack in the corner)