Judging by all the current listings for UPS delivery for this show, it's pretty safe to assume you will be fine. Just because the venue says the show is mobile only doesn't mean that there weren't any hard tickets. Season ticket holders, fan club, presales, etc. sometimes have other delivery methods available to them. While the general onsale on Ticketmaster was mostl likely mobile only, that doesn't mean all tickets were sold like that. I wouldn't worry myself over it.
I understand your concern but the people that you talk to at the venues are generally front line people that don't know all the details. Again, like I said the sales may be mobile only online but I'm sure if people bought tickets at the venue on the day of the onsale, the venue was printing the tickets for them (among other types of sales I mentioned previously). Someone won't be shipping you paper tickets via UPS that aren't valid. Plus, there wouldn't be 15 ticket listings currently on StubHub selling via UPS if they weren't getting them that way.
Hey @Jeanine1! As ticketmvp was saying, some users may have different forms of delivery available to them and there is no need to worry. You are always covered under our FanProtect Guarantee as well, and we back and cover all tickets on our site. In the very rare case, there is an issue, we will find you comparable replacements or your money back. If you have any other questions or concerns, feel free to send me a private message at any time.