Student Workbook Data Lost After Reassigning

Yesterday, I had already assigned my workbook to my student and they completed the task. I could see their results before. However, today i mistakenly reassigned the same workbook to one of the students in the same group/class. After doing so, all of the previous data/result from my students disappeared and I am no longer able to access them. 

Is there any way to recover the lost student data? It is veru important for my evaluation and reporting. 

Thank you so much in advance for your support. I truly hope there is a way to restore the data.