They may have customised their privacy settings to limit the amount of personal info you can see on them - including stickers they've received.
Can't see a sticker you sent on MeetMe.com?
Firstly, I'd recommend checking that you've sent the sticker correctly. Here's what their help section says about sending stickers:
If you're still feeling stuck though, you can use the "suggestion" link at the bottom of their homepage to get in touch with a member of their team."MeetMe profiles by default are available for other members of the MeetMe community to view. To restrict who can view your profile, click on the "Settings" link in the upper right-hand corner of the page. Under the "Privacy" tab is the setting "Who can view my profile?" Choose your desired level of privacy, then make sure to click the "Save" button to confirm your selection."
