When sending an MMS or SMS (not the quick version) ... there should be a SAVE draft option so you can come back to it and it should just sit in the campaign area as DRAFT ... https://dashboard.clicksend.com/#/mms/campaigns | https://dashboard.clicksend.com/#/sms/campaigns
Also if the above can happen ... you should be able to do a TEST preview before a final is approved ... You will notice that if you need to send a test (you actually have to repeat the process before you send the final which can cause mistakes when you are copying and pasting again)