Answer: I believe you pinched off the only growing bud on the plant. Foxgloves can produce multiple rows of bloom on each stem, but can't be forced to produce multiple stems by pinching. You can successfully pinch back snapdragons after they form 4-6 sets of leaves to promote branching, but not so with foxgloves. I'm sorry for the bad news.
Pefore pinching back any seedling, make sure that type of plants is amenable to pinching back, and always wait until seedlings have several sets of leaves before pinching back, as the axillary buds (side-buds) are on the stem where the leaves attach. Hope this helps!
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