When you ready a spell, you cast it as normal but hold its energy, which you release with your reaction when the trigger occurs.
the same page:
When the trigger occurs, you can either take your reaction right after the trigger finishes or ignore the trigger.
The spell is cast and is waiting to be released. If you ignore all possible triggers, what happens with the spell? Does it dissipate without a trace?
Another question handles the scenario of ignoring just one (or some number) of triggers, but I'm wondering what happens if you ignore all triggers.