Should a property search have revealed that a neighbour had planning permission to build a house in his back garden even though this planning permission had expired. Because they have applied for new permission saying that the plans were previously passed.
When a local search is done on a property is usually relates to the property being bought itself and doesn't usually pick up on anything else unless the addresses are vague and come up on the records when the property bought is searched for.
There are other additional searches which could have been done but they are not standard in normal conveyancing practice.
Did you raise any specific questions with your solicitor about any development or ask for any specific searches or enquiries to be made.
Also worth checking if anything was mentioned on the property info provided when you bought.
In your favour you may find by contacting the local council that your neighbours application no longer meets all the current requirements regarding building regulations and local planning schemes. he will have to apply again in any case with up to date plans and that gives you and your other neighbours time to examine the plans and make any objections, the council can't automatically give consent on out of date plans.