Puchasing anything through Ukraine is unviable at the thought level from the perspective of Russian army. Hence why it's much more likely to come from elsewhere.
Using VPN for what purpose exactly? VPN won't deliver you a device from Ukraine. VPN won't change your physical location.
Russian military was using Ukraine's own mobile operators and its talks has been recorded (and locations discovered probably) many times thanks to that. Yes, they are stupid enough to not know about messengers sometimes.