Hello there Joana,
don’t worry to much- mistakes happen. Yes: when you have a foundationless frame you have to be very careful how you hold it- It needs to be kept in a vertical orientation as it is very delicate and will break easily if gravity can pull it to either side. As you found. Once it has been attached at the sides and the bottom it become much stronger- after a year of use in a brood box it will be very strong once bee cocoons have strengthened the wax.
So- it sounds to me like you just have a gap where it was - and the easiest solution would be to slip in a new frame of foundation with wires. You could also put in a plastic frame coated with wax in a pinch (I prefer natural but plastic does work too).
You could salvage the comb as dawn has suggested by rubber banding it into an empty wooden frame: however it takes a little skill and maybe reading to work out how to do this well- and it depends ont he state of the piece/s of comb if it is worth it or not.
To see how rubber banding should be done- the video linked int he article below shows the best method I have ever seen- the trick is the rubber bands he uses to push the comb pieces up to the top bar of the frame. I have copied this method with brilliant results. After the bees repair an re-attach the comb they chew the bands off and throw them out the front door of the hive: