[souffle]

It does sound as if the infection has caused irritation of the bladder leading to leaking when he is asleep. Older hamsters do tend to drink more and produce more dilute urine as they weaken with age. Immune systems are also weaker and they get prone to infections. I've not seen the penile plug myself but hopefully the meds should get rid of that. They can also get crystals in the bladder so make sure he can still wee as a blockage is a medical emergency. Keep changing the wet bedding out for him so he doesn't get skin problems from urine.