Jo .....
Thank goodness you are OK! I guess it takes a scare like you had to remind us that the imbalance is ever present on some level for most of us.
Although I no longer use a cane, I have learned when I have to be extra careful. Large crowds of people really throw me for a loop. It seems I have no stable visual source in that situation and I always try to stay near a stable object, e.g. wall, railing, furniture, etc. I always grab a cart in a parking lot to push in a store and keep it until I am back out in the lot. However, from what you are describing it was the leaning over to pick up the soda drink that was your undoing. I always try to hang onto something or lean up against something before leaning over.
One of the vestibular exercises I was told to do is stand in the corner of my kitchen cabinets, with feet slightly apart. Then I take an object (bottle, cone, whatever) and bend down to my left foot, bring it back up above my head to the right, keeping my eyes steadily on the object. Then reverse, lower right to upper left and then low center to above head center ..... always keeping eyes on the object. Do it slowly at first, increasing speed as you can without getting dizzy. The point is to do it as fast as you can to just before getting dizzy. Slow down if you start getting dizzy. Do it 10 times in succession each direction (total of 30 bends each repetition). I have found this exercise has greatly improved my imbalance when standing back up again from leaning over.
Be careful and let us know how you are doing.
Clarice