The easiest solution would be to consult the heads of your department which is where you received your former team member from and ask if you could get a replacement. This would seem like the best solution because obviously there are other individuals in the company who have the required set of skills for the job. Another potential solution would be for you to fill the void yourself partially. This is not ideal at all as you already have a great deal of responsibilities trying to manage the entire project from start to finish but since you know how to do at least some of the work, you could complete some of the tasks until you find a more permanent solution. Getting some of the tasks done is better than not getting any of it done. Also, another idea would be to divide up the work between the remaining members of your team. Try to separate the work based on who can do each task and ensure that everybody is compensated for the additional work. Ensure that everyone who is involved is doing the same amount of additional work more or less. If you could automate some of the work, then that would help mitigate the pain and loss.