Hello Dixie. My name is Marc. I'm a licensed attorney and I will be happy to assist you today.
First of all, I'm sorry this happened to you and I wish you a speedy and full recovery. Home Depot seems to have had no basis for denying your claim simply because you didn't report the accident right away. After a fall like this, most people like you, me and others may feel some pain, a bit stunned, very annoyed and a little embarrassed maybe. But we get up, try to shake it off and go on with our lives. It is not uncommon, however, for symptoms of injury to manifest themselves at a later time. And in your case - "a few days" later is quite reasonable.
HD's policy of requiring you to report the accident sooner is not only unfair to you, it is counter productive. After all, does HD want its employees to immediately file reports after ever fall, bump or knock even if the employee doesn't feel injured? In sum, HD's policy is unreasonable and your claim should not be barred simply because you waited a few days before reporting the accident.
The more salient point here is this: Based upon what you've told me, you (1) fell on ice (2) in the HD parking lot (3) while on your way home from work, and (4) you sustained injury as a result.
At the very least, you have the same rights as a customer who slips on ice in the HD lot. HD owes a duty to customers and employees to keep its parking lot and store free from hazardous conditions (which includes snow and ice accumulation). In your case, you have a cause of action for premises liability against HD because it failed in its duty to keep the lot free of ice. Furthermore, you were injured as a result.
Now, you are an employee and this accident happened while you were on the job (going to your car after work is still considered to be on the job in this case). Thus, you are entitled to workers' comp and/or other disability benefits provided through your employment. In other words, this was a work-related accident. Moreover, it was caused by HD's negligence.
It is not for HD to determine whether you were injured or whether your injuries are related to this accident. It sounds like you have ample, quality evidence from your doctors that establish that your injuries are causally related to this accident. Thus, they have no basis to deny your claim on grounds that your injuries are unrelated to your work. And your pre-existing conditions also do not preclude relief since this accident clearly exacerbated any previous injuries. Also - you have two witnesses and, probably, a recording from a surveillance camera to establish that the accident occurred and its causal relation to your injury.
Ultimately, you should probably hire a local workers compensation or other attorney who specializes in work-related accidents or premises liability. You might try reasoning with HD yourself, asserting the points and arguments I mention above. I always thought HD was a good employer, but maybe I'm wrong. Under the circumstances, HD should not deny your claim.
Accordingly, my suggestion is to (1) contact the HD benefits department and try to reason with them as described above, and (2) if HD still denies your claim, contact an attorney who can advocate for you and get you workers comp, other disability payments, or civil damages for your injury and lost wages.
I hope I have provided you with useful information that helps you better understand your issues and options. Please let me know if you have any further questions. Otherwise, please feel free to rate my answer, as that is the only way I can receive credit.
Feel better soon!