Most Helpful Guy
It's not weird really, no. It's kind of natural to be interested. Just ask him if he's been seeing anyone since you guys were together, unless you already know he has then ask if he's seeing anyone right now.
Most Helpful Girl
Just assume he does b/c you found him hot enough to date... ergo... others will take him off the shelf as you did
otherwise, he'll think you are poking him with a stick, invading private space in which no longer invited = could lead to him saying
mind your own business
or rub all her good qualities in your face (even if he has to invent a GF)