The approach to finding data on mobile check deposits, or Remote Deposit Capture (RDC) activity, will depend on what systems and processes are used to post them to the member’s account.
If deposits are automatically posted:
Check out Tool #1985 Auto-Post RDC Deposit Dashboard to find a listing of every posted deposit (or attempts that ended in error), for any date or time period you are interested in. Total amount and number of checks are included for quick reference. Interested query-writers can find source data in table RDCTRNTRK.
If deposits are batch-posted or manually posted:
Query the data table TRANS1 (current month), or HTRANS1 (historical months), making sure to organize (sort) the data by Activity Date. 
To pick out the RDC transactions, focus on Origin Code and Transaction Description information. Recorded data for these will be different for each credit union and should be researched to use the right information for your own. Typically, data is found to be 04 (but may be 08) for Origin Code, and include one or more of the words “MOBILE”, “REMOTE”, or “RDC” in the description.