[souffle]

Constipation is very unusual in hamsters as they eat such a high fibre diet.
New hamsters will often poop in the nest or near it until they settle. The going in the corner is usually when the wee and they lift the tail and sort of look like they strain to urinate. Poops are usually done anywhere really. They are quite dry and inoffensive and they often drop to the bottom of the substrate as they are heavier than it so check down there. If he is eating and drinking and behaving normally I wouldn't worry.
Check you haven't given fluffy or cotton pod type bedding as this can cause blockages.