Whenever an attack is there, a lot of things can be happened. Constructions stop advancing and so do market transactions.
However, when you are getting scouted, they do not. If you want them to believe you have no Gold or Resources, try the following trick:
You can hide your Gold and Resources in the Market
You can open your Marketplace by clicking on the Market building.
Put all your Resources into the Market. (To be able to create multiple transactions, you will need a higher level Market)
Make sure you put the unit price of all Resources at a ridiculously high unit price. For instance - 10 unit price. No one will buy at this price level (and if they do your hardly going to complain), and your Resources will be hidden since they will be subtracted from your supply the instant you post the request in the Market.
It costs a minor amount of Gold to create transactions, but can be worth it to outwit the scout and make them think they found a 'worthless farm', which would be your city).
Note that if your troops are in the city, do not bother doing transactions!
Hiding Troops and Resources in the Wilderness.
Go to one of your Wilderness which you wish to use and click on it
Click reinforce OR go to your Rally Point and click Reinforce from the top drop down tab.
Send all your troops with all extra (Resources which your Storehouse can't keep safe] Resources out of your city.
Many players send their troops to a far away Wilderness they have conquered so that it is harder to be found.
There are always other Players actively raiding Wildernesses searching for Crests which can be found in higher level Wilderness (5-10). If your Army is massive enough, you may get away with it if you accidentally get scouted. If they send their army to the Wilderness you are located in without scouting first, you may end up losing a couple men. Most players just send a minor army to an already occupied Wilderness, assuming there will be no Army stationed.
Keep in mind that if another player clicks on the Wilderness your Army is camped at, they will see that it belongs to you and if they are actively seeking your Army, this may lead to a loss of your Army.
This strategy alone is a very good reason to A) build LOTS of supply wagons early on... tens of thousands of them... and B) keep your wilds approximately 100 squares away from your city, and even then, not all in the same place. Also, when hiding your resources in wilds, keep in mind that you STILL have to have enough food to keep those wagons alive! You can't feed them with food you sent with them (apparently they are so loyal that they'd rather die than open the contents of their wagon, much like Jason Statham in the Transporter).
To defend or not to defend?
Simple question is that resolves itself to whether or not you feel you can adequately fend off your foe. Without a high enough level watchtower and research in Eagle Eyes, you won't have the information you need to make this decision, so keep that in mind when planning your city.
Manytimes it does not make sense to defend against a foe who might simply be trying to farm you once per day, and won't permanently cripple your forces. If your army is paltry compared to the enemy, stick with sanctuary mode, bide your time, and use a Portal of Refuge or a Portal of Order if you absolutely have to, to hide your city elsewhere and make its location unknown via the Mists of Avalon.
If your forces seem equal or even somewhat close to that of the attacker, consider riding it out and defending against the attack. If you can kill all of the opposing forces, there's a good chance the attacker won't come back-- nobody enjoys suicide all of their troops, not knowing how many reinforcements you might have.
Please keep in mind that you do not necessarily need an equal number of troops in order to successfully defend. Walls and wall defenses play a big role, as well as the types of troops being sent by the enemy. To put this into perspective, in one domain this author was able to kill well over two million archers and five hundred thousand ballistae using scarcely more than five hundred thousand archers and one hundred thousand ballistae of his own when three top-ten alliances attacked him at the same time.