Nothing is lost.
PlanbookEdu does not delete plans or remove accounts unless you specifically ask us to.
When a trial ends and you choose not to subscribe, your account moves to the free version. You keep signing in with the same address, and every plan you wrote during the trial is still there.
What changes
You lose the Premium-only features — copying planbooks, multiple planbooks at once, exporting to Word and PDF, spell check, collaboration, recovering deleted plans. See Free vs. Premium for the full list.
Plans written using those features don't disappear. A planbook you created by copying is still yours; you just can't make another copy until you subscribe.
If you subscribe later
Everything comes back, and your plans are where you left them. There's no penalty for a gap and nothing to restore — see Subscribe to Premium.
Getting your plans out anyway
If you'd like a copy for your own records, export before the trial ends while you still have Premium — see Export an entire planbook.
Worth doing if it gives you peace of mind, though it isn't necessary: your plans stay in the account either way.