Okay so working in Retail, I often get really bored and if a customer starts chatting with me, I don't mind chatting away. Sometimes, we actually get bored enough that we start trying to make conversation. I've said a lot of things to customers I wouldn't usually talk about (traffic conditions, children's toys, old movies etc) because they've ignited a conversation and to be frank, I seem 100% interested when I really don't care
But I genuinely answer because it's boring as hell doing the same job over and over. So to figure out whether he's interested or not, is to go back to the store and look around. If he's working in an area, sort of float around. Don't go up to him straight away, but kinda look a bit confused at the products. If he notices you, wait to see if he asks if you need help. If not, wait till he's doing something else and then ask him for help. Don't cling to him as soon as you can tell he ain't stoppin.
If he's at the counter, bring the product to him and ask about it. Or buy it if you want it, and mention that you forgot it last time you were here, and that you were pissed off when you got it home and it was missing etc. and just sort of make a self-depreciating joke. People find it a bit cute
If he again, makes an effort to talk again, maybe make a joke like "maybe I'll see you at my work soon" and if he responds nicely leave it, and if he pulls a more friendly gesture, throw in "or maybe just in general" and leave it there also. Then go back a third time, just browsing and if he starts a convo or makes an effort to recognise you, just sort of ask if you wanna get a drink. Don't act flirty or anything. Just casually. He'll get the message without being put on the spot
That's the BEST I could come up with because I understand that you're shy
i love you haha... I laugh so hard at this