Sounds scary! Was it an Allan key by any chance? I've done a fair share of bicycle repairs, and never had a problem after investing in a proper set of allan keys[1]. Several times I or friends have rounded the slot with a cheap tool, but fixed it just by trying again with the better tool.
Glad your bike was okay in the end.
[1] - https://wheelfanatyk.com/blogs/blog/wera-nails-it