I've never heard of that payment processor before, the second google search result is "scam!!" but more useful is this post on a forum that payments can be reversed:
I got some useful news for STP
I don't know this is true or not but we can file a dispute and get my money back when make a compalints to STP investigation admin
I got this news from Hyipingmoney admin
QUOTE
Message: Hi Everyone, If you have been scammed by any HYIP program AND you pay your deposit using Solid Trust Pay, please email "investigations@solidtrustpay.com" to initiate complaint against that HYIP's STP username. Let Solid Trust Pay know about this. STP will only freeze/suspend the account if at least 5 individuals make the disputes.Hopefully, you all can get your monies back. YOU MUST DO THIS ASAP BEFORE THEY SHUT DOWN THE WEBSITE!!!!! PLEASE SPREAD THIS!!!!Also note that they take credit cards, this is an immediate red flag, as a dispute with the credit card company by the buyer will yank the money back out on any of these types of services. They also seem to have the same issues as other processors: payments take considerable time to be withdrawn to any funding method, and the mystery fund lock with months to verify.