Loosing one's follow list seem to be a rather common issue on Nostr, which has been discussed multiple times, indeed.

You need to fetch your kind3 notes.

For example, from two months ago this is still available (you need to check the "p" tags, not the relay list): nostr:note1jafr5pq8tec92a00xsgtmwyt56ynp0raf3gxrps5pewps4c3tahq2eew4s