It's amazing how many people don't. I've seen tons of people who talk the backup talk, but don't walk the backup walk. Until they've been bitten and really needed something they just lost. Luckily, my "bite" came well over a decade ago and I've been backing up religiously since.
If it's not something easy like /home simply being unmounted, follow pixellany's advice. Don't do anything that would write to the disk. Run down to the store and buy yourself a brand new disk, then dd the entire old one to the new (don't mix up your "if=" and "of="!!!) Totally disconnect the old and attempt all recoveries using only the new.
If is just /home not being mounted, consider this your personal "bite" ... luckily a small one. Start backing up. If it's a real problem, your bite might be a major "ouchie", but do what you can (on a copy!) and learn from the situation. I hope things turn out well for you!